Nickel manganese composite hydroxide particles and manufacturing method thereof, cathode active material for a non-aqueous electrolyte secondary battery and manufacturing method thereof, and a non-aqueous electrolyte secondary battery

ABSTRACT

Provided are nickel manganese composite hydroxide particles having a small and uniform particle size and having a double structure which enables to obtain a cathode active material having a hollow structure, and a manufacturing method thereof. When obtaining the nickel manganese composite hydroxide by a reaction crystallization, using an aqueous solution for nucleation, which includes at least a metallic compound that contains nickel, a metallic compound that contains manganese and an ammonium ion donor and controlling the pH value that is measured at a standard solution temperature of 25° C. is 10.5 to 12.0, nucleation is performed in an oxidizing atmosphere in which the oxygen concentration is greater than 1% by volume, and then nuclei are grown by switching the atmosphere from the oxidizing atmosphere to a mixed atmosphere of oxygen and inert gas in which the oxygen concentration is 1% by volume or less.

TECHNICAL FIELD

The present invention relates to nickel manganese composite hydroxideparticles and the manufacturing method thereof, cathode active materialfor a non-aqueous electrolyte secondary battery, which uses the nickelmanganese composite hydroxide particles as an ingredient, and themanufacturing method thereof, and a non-aqueous electrolyte secondarybattery that uses the cathode active material for a non-aqueouselectrolyte secondary battery as the cathode material.

BACKGROUND ART

In recent years, as portable electronic devices such as mobiletelephones and notebook personal computers become widespread, there is alarge need for development of compact and lightweight non-aqueouselectrolyte secondary batteries that have high energy density. Moreover,there is also a strong need for development of a high-output secondarybattery as a motor drive battery, and particularly, as a battery for thepower source of transport equipment.

As a secondary battery that satisfies this kind of need is a lithium-ionsecondary battery. A lithium-ion secondary battery comprises an anode, acathode and an electrolyte, and a material in which lithium can bedesorbed and inserted is used as the active material for the anode andcathode.

Currently, much research and development is being performed related tolithium-ion secondary batteries, and of that, research of lithium-ionbatteries that use lithium metal composite oxide having layeredstructure or spinel structure as the cathode material has been advancingas high-energy density batteries that are capable of 4V class highvoltage.

Currently, as the cathode material of that kind of lithium-ion secondarybattery, lithium metal composite oxides such as lithium cobalt compositeoxide (LiCoO₂) having a relatively simple composition, lithium nickelcomposite oxide (LiNiO₂), which uses nickel that is less expensive thancobalt, lithium nickel manganese cobalt composite oxide(LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂), lithium manganese composite oxide(LiMn₂O₄) that uses manganese, and lithium nickel manganese compositeoxide (LiNi_(0.5)Mn_(0.5)O₂) have been proposed.

Even of these cathode active materials, lithium nickel manganesecomposite oxide (LiNi_(0.5)Mn_(0.5)O₂), which is high capacity, hasexcellent thermal stability and does not use cobalt of which there arefew reserves, has gained much attention in recent years. Lithium nickelmanganese composite oxide (LiNi_(0.5)Mn_(0.5)O₂) is layered in the sameway as lithium cobalt composite oxides and lithium nickel compositeoxides, and nickel and manganese are included in transitional metalsites at basically a compositional ratio of 1:1 (see Chemistry Letters,Vol. 30 (2001), No. 8, p. 744).

Incidentally, as a condition for a lithium ion secondary battery toobtain good performance characteristics (high cyclability, lowresistance, high output) cathode material comprising particles having auniform and suitable particle size is required.

This is because, when a cathode material having a large particle sizeand low specific surface area is used, the reactive area with theelectrolyte cannot be sufficiently maintained, so the reactionresistance rises, and it is not possible to obtain a battery having highoutput. Moreover, when a cathode material having a wide particle sizedistribution is used, the voltage applied to the particles in theelectrode become uneven, and when the battery is repeatedly recharged,small particles selectively deteriorate, and the capacity decreases.

In aiming for high output of a lithium-ion secondary battery, shorteningthe distance between the cathode and anode is effective, so preferablythe cathode plate is made to be thin, and from this aspect as well,using cathode material having a small particle size is useful.

Therefore, in order to improve the performance of the cathode material,it is important that lithium nickel manganese composite oxide, which isa cathode active material, be manufactured so that the particle size issmall and uniform.

Lithium nickel manganese composite oxide is normally manufactured fromcomposite hydroxide, so in order to make the lithium nickel manganesecomposite oxide particles small with a uniform particle size, it isnecessary to use a composite hydroxide as the raw material that hassmall particles with a uniform particle size.

In other words, in order to improve the performance of the cathodematerial and manufacture a high-performance lithium-ion secondarybattery as a final product, it is necessary to use a composite hydroxidethat comprises particles having a small particle size and narrowparticle distribution as the composite hydroxide that will become theraw material of the lithium nickel manganese composite oxide used informing the cathode material.

As a nickel manganese composite hydroxide that is used as the rawmaterial of a lithium nickel manganese composite oxide, manganese nickelcomposite hydroxide particles are proposed in JP2004-210560(A) which arecomposite hydroxide particles having a manganese to nickel ratio of 1:1,with an average particle size of 5 to 15 μm, tap density of 0.6 to 1.4g/ml, bulk density of 0.4 to 1.0 g/ml, specific surface area of 20 to 55m²/g, amount of sulfate contained being 25 to 45 weight %, and in X-raydiffraction, a ratio (I₀/I₁) of the maximum strength (I₀) of the peak inthe range 15≤2θ≤25 and the maximum strength (I₁) of the peak in therange 30≤2θ≤40 of 1 to 6. The secondary particle surface and internalstructure is formed in a netlike structure with fold-like walls ofprimary particles, with the space surrounded by the fold-like wallsbeing relatively large.

Furthermore, as the manufacturing method, a method is disclosed inwhich, while keeping the amount of oxidation of manganese ions within aset range, a mixed aqueous solution of manganese salt and nickel salthaving an atomic ratio of manganese and nickel of 1:1 is mixed andreacted with an alkaline solution in an aqueous solution having a pH or9 to 13 with the existence of a complexing agent to causecoprecipitation of particles.

However, in the case of the lithium manganese nickel composite oxide andmanufacturing method disclosed in JP2004-210560(A), although thestructure of the particles is considered, it can be clearly seen in thedisclosed electron micrograph that coarse particles and fine particlesare mixed together in the obtained particles, and making the particlesize uniform has not been considered.

On the other hand, in regards to the particle size distribution oflithium composite oxide particles, a lithium composite oxide has beendisclosed in JP2008-147068(A) such that in the particle sizedistribution curve, the particles have a particle size distribution withan average particle size D50, which means the particle size of acumulative frequency of 50%, of 3 to 15 μm, a minimum particle size of0.5 μm or greater, and a maximum particle size of 50 μm or less, andwhere in the relationship between average particle size D10 at acumulative frequency of 1.0% and D90 at a cumulative frequency of 90%,the ratio D10/D50 is 0.6 to 0.9, and the ratio D10/D90 is 0.30 to 0.70.It has also been disclosed that this lithium composite oxide has highrepletion, excellent charge and discharge characteristic and high outputcharacteristic, and does not easily deteriorate even under conditions ofa large charge and discharge load, so by using this lithium compositeoxide, a non-aqueous electrolyte lithium ion secondary battery havingexcellent output characteristics and little deterioration of cyclabilitycan be obtained.

However, the lithium composite oxide disclosed in JP2008-147068(A)includes fine particles and coarse particles as seen from the fact thatit has a minimum particle size 0.5 μm or greater and a maximum particlesize of 50 μm or less with respect to an average particle size of 3 to15 μm. The above particle size distribution that is regulated by D10/D50and D10/D90 is not a narrow particle size distribution range. In otherwords, the lithium composite oxide of JP2008-147068(A) can be said tohave sufficiently high uniformity of particle size, and when thatlithium composite oxide is used, an improvement in performance of thecathode material cannot be expected, and it is difficult to obtain anon-aqueous electrolyte lithium-ion secondary battery having sufficientperformance.

Moreover, a method for manufacturing a composite hydroxide that willbecome the raw material for a composite oxide aimed at improving theparticle size distribution has been disclosed. In JP2003-086182(A), in amethod for manufacturing a cathode active material for a non-aqueouselectrolyte battery, a method for obtaining a hydroxide or oxide as aprecursor is disclosed in which an aqueous solution containing two ormore kinds of transition metal salts or two or more kinds of aqueoussolutions of different transition metal salts is put into a reactionvessel together with an alkaline solution, and co-precipitation isperformed while causing the solution to coexisting with a reducing agentor by passing an inert gas though the solution.

However, the technology disclosed in JP2003-086182(A) is for recoverywhile classifying the generated crystals, so in order to obtain amaterial having uniform particle size, strictly managing themanufacturing conditions is considered to be necessary, so production onan industrial scale is difficult. Moreover, even though it is possibleto obtain crystal grain having a large grain size, obtaining smallparticles is difficult.

Furthermore, in order to make a battery with high output, increasing thesize of the reactive area without changing the particle size iseffective. In other words, by making particles that are porous, or thathave a hollow particle structure, it is possible to increase the surfacearea that contributes to the battery reaction, and it is possible toreduce the reaction resistance.

For example, in JP2004-253174(A) cathode active material for anon-aqueous electrolyte secondary battery comprising a lithiumtransition metal composite oxide at least having a layered structure isdisclosed wherein the lithium transition metal composite oxide compriseshollow particles having a shell section on the outside and a hollowsection on the inside of the outer shell section. Also disclosed is thatthis cathode active material for a non-aqueous electrolyte secondarybattery has excellent battery characteristics such as cyclecharacteristics, output characteristics, thermal stability and the like,and can suitably be used for a lithium-ion secondary battery.

However, JP2004-253174(A) makes no mention of particle size of thecathode active material, while the cathode active material compriseshollow particles and therefore these particles are expected to have agreater specific surface area than solid particles. Therefore,improvement in reactivity with the electrolyte due to an increase inspecific surface area can be expected, however, the effect on themigration distance of the lithium ions due to making the particlessmaller is not clear; and a sufficient improvement in outputcharacteristics cannot be expected. Furthermore, in regards to theparticle size distribution, the particle size distribution is consideredto be the same as in conventional cathode active material, so selectivedeterioration of minute particles due to uneven voltage that is appliedinside the electrodes occurs, and there is a strong possibility thatthere will be a drop in battery capacity.

As described above, currently neither a lithium composite oxide that cansufficiently improve the performance of a lithium-ion secondary battery,nor a composite hydroxide that will become the raw material for thatcomposite oxide have been developed. Moreover, after investigatingvarious methods for manufacturing composite hydroxides, currently amethod that is capable on an industrial scale to manufacture a compositehydroxide that can become the raw material for a composite oxide capableof improving the performance of a lithium-ion secondary battery has notbeen developed. In other words, a cathode active material havingparticles with a small and uniform particle size, and that have a largereactive area, for example having a hollow structure, remains to bedeveloped, and a method capable of industrially manufacturing that kindof cathode active material is desired.

RELATED LITERATURE Patent Literature

-   [Patent Literature 1] JP2004-210560(A)-   [Patent Literature 2] JP2008-147068(A)-   [Patent Literature 2] JP2003-086182(A)-   [Patent Literature 4] JP2004-253174(A)

Non-Patent Literature

-   [Non-patent Literature 1] Chemistry Letters, Vol. 30 (2001), No.    8, p. 744

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In consideration of the problems above, an object of the presentinvention is to provide nickel manganese composite hydroxide particlesthat, when used as a raw material, a lithium nickel manganese compositeoxide is obtained that has small particles with a uniform particle sizeand that have a high specific surface area due to a hollow particlestructure thereof.

Moreover, another object of the present invention is to provide acathode active material for a non-aqueous electrolyte secondary batterythat can reduce the value of the cathode resistance that measured whenused in a battery, and to provide a non-aqueous electrolyte secondarybattery that uses that cathode active material and that has highcapacity, good cyclability and high output.

Furthermore, another object of the present invention is to provide amethod for industrially manufacturing the nickel manganese compositehydroxide particles and cathode active material.

Means for Solving the Problems

The inventors diligently gave thought to the structure of lithium nickelmanganese composite oxide which is capable of displaying excellentbattery characteristics when used as a cathode material for a lithiumion secondary battery, and as a result, learned that by controlling theparticle size distribution of nickel manganese composite hydroxide,which is the raw material, and by giving the nickel manganese compositehydroxide the structure with a center section comprising fine primaryparticles and an outer shell section on the outside of the centersection comprising of primary particles that are larger than the primaryparticles of the center section, it is possible to obtain lithium nickelmanganese composite oxide having hollow structure and comprising smallparticles with a highly uniform particle size. Moreover, it was learnedthat the nickel manganese composite hydroxide can be obtained bydividing crystallization process into a nucleation step and a particlegrowth step by controlling the pH in the crystallization process and bycontrolling the atmosphere of each step. The present invention wasachieved based on the above technical knowledge.

A manufacturing method for manufacturing nickel manganese compositehydroxide of the present invention is to manufacture nickel manganesecomposite hydroxide particles using a reaction crystallization, thenickel manganese composite hydroxide particles being expressed by ageneral formula of Ni_(x)Mn_(y)Co_(z)M_(t)(OH)_(2+a) (where x+y+y+z+t=1,0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, 0≤a≤0.5, and M is one or moreadded elements that are selected from among Mg, Ca, Al, Ti, V, Cr, Zr,Nb, Mo and W), and

the manufacturing method of the present invention comprises:

a nucleation step of controlling an aqueous solution for nucleation,which includes at least a metallic compound that contains nickel, ametallic compound that contains manganese, and an ammonium ion donor, sothat a pH value thereof that is measured at a standard solutiontemperature of 25° C. is 12.0 to 14.0, and causing nucleation in anoxidizing atmosphere having an oxygen concentration of greater than 1%by volume; and

a particle growth step of controlling an aqueous solution for particlegrowth, which includes nuclei formed in the nucleation step, so that apH value thereof that is measured at a standard solution temperature of25° C. is 10.5 to 12.0, and causing nuclear growth by switching from theoxidizing atmosphere to a mixed atmosphere of oxygen and inert gashaving an oxygen concentration of 1% by volume or less within a range of0 to 40% of the overall time of the particle growth step from the startof particle growth step.

Preferably, the oxygen concentration in the oxidizing atmosphere is 10%by volume or greater, however, on the other hand, the oxygenconcentration in the mixed atmosphere is 0.5% by volume or less.

Preferably, switching in the particle growth step from the oxidizingatmosphere to the mixed atmosphere of oxygen and inert gas is performedwithin a range of 0 to 30% of the overall time of the particle growthstep from the start of the particle growth step.

The aqueous solution for particle growth is obtained by adjusting the pHvalue of the aqueous solution for nucleation after the nucleation stephas finished. Alternatively, the aqueous solution for particle growth isobtained by adding the aqueous solution for nucleation, which containsthe nuclei formed in the nucleation step, to a solution that is separatefrom the aqueous solution for nucleation with the formed nuclei.

Furthermore, preferably, in the particle growth step, part of a liquidpart of the aqueous solution for particle growth is excreted.

Moreover, preferably, in the nucleation step and the particle growthstep, a temperature of the aqueous solution for nucleation and forparticle growth is maintained at 20° C. or greater, and an ammoniaconcentration of the aqueous solution for nucleation and for particlegrowth is maintained within a range of 3 to 25 g/L.

Furthermore, in order to manufacture nickel manganese compositehydroxide particles that includes the one or more added elements, in thenucleation step and particle growth step, preferably, an aqueoussolution, to which a salt that includes the one or more added elementsare dissolved, is added to a mixed solution that includes a metalcompound that contains nickel and a metal compound that containsmanganese; or an aqueous solution in which a salt containing the one ormore added elements are dissolved and the mixed aqueous solution aresupplied at the same time to a crystallization tank that stores anaqueous solution before reaction that includes at least the ammonium iondonor in order to form the aqueous solution for nucleation.Alternatively, it is also possible to coat the nickel manganesecomposite hydroxide particles that were obtained in the particle growthprocess with the one or more added elements. As the coating method,there is a method of adding an aqueous solution that includes the one ormore added elements to a solution in which the nickel manganesecomposite hydroxide is suspended, while controlling a pH thereof to aspecified value, and then causing precipitation on a surface of thenickel manganese composite hydroxide particles, or there is a method ofspray drying a slurry in which nickel manganese composite hydroxideparticles and a salt that includes the one or more added elements aresuspended, or there is a method of mixing nickel manganese compositehydroxide particles with a salt that includes the one or more addedelements using a solid phase method.

The nickel manganese composite hydroxide particles of the presentinvention are expressed by the general formula ofNi_(x)Mn_(y)Co_(z)M_(t)(OH)_(2+a) (where x+y+z+t=1, 0.3≤x≤0.7,0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, 0≤a≤0.5, and M is one or more addedelements that are selected from among Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Moand W), and are spherical shaped secondary particles that are formed bya plurality of aggregate primary particles, and the nickel manganesecomposite hydroxide particles of the present invention is characterizedin that the secondary particles have an average particle size of 3 to 7μm, a value [(d90−d10)/average particle size], which is an indexindicating an extent of particle size distribution thereof, of 0.55 orless, the particles have a center section comprising fine primaryparticles, and an outer shell section on the outside of the centersection comprising plate shaped primary particles that are larger thanthe fine primary particles.

Preferably, the fine primary particles have an average particle size of0.01 to 0.3 μm, the plate shaped primary particles that are larger thanthe fine primary particles have an average particle size of 0.3 to 3 μmand a ratio of the thickness of the outer shell section with respect tothe particle size of the secondary particles is 5 to 45%.

Moreover, preferably, the one or more added elements are uniformlydistributed inside the secondary particles and/or uniformly cote thesurface of the secondary particles.

Preferably, the nickel manganese composite hydroxide particles of thepresent invention are manufactured by the manufacturing method of thepresent invention for manufacturing nickel manganese composite hydroxideparticles.

A manufacturing method for manufacturing cathode active material of thepresent invention is to manufacture a cathode active material for anon-aqueous electrolyte secondary battery for a non-aqueous electrolytesecondary battery comprising lithium nickel manganese composite oxidehaving a layered hexagonal crystal structure and expressed by thegeneral formula of Li_(1+u)Ni_(x)Mn_(y)Co_(z)M_(t)O₂ (where−0.05≤u≤0.50, x+y+z+t=1, 0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, M isone or more added elements that are selected from among Mg, Ca, Al, Ti,V, Cr, Zr, Nb, Mo and W), and

the manufacturing method comprises:

heat treatment of the nickel manganese composite hydroxide particles ofpresent invention as raw material at a temperature of 105 to 750° C.;

a mixing step that mixes a lithium compound into the heat treatedparticles to form a lithium mixture; and

a calcination step that performs calcination of the mixture formed inthe mixing step in an oxidizing atmosphere at a temperature of 800 to980° C.

Preferably, the lithium mixture is adjusted so that a ratio between thesum of the number of metal atoms other than lithium included in thelithium mixture and the number of lithium atoms is 1:0.95 to 1.5.

Moreover, preferably, in the calcination step, temporary calcination hasalready been performed before calcination at a temperature of 350 to800° C.

Furthermore, preferably, the oxidizing atmosphere during the calcinationstep is an atmosphere having an oxygen content of 18 to 100% by volume.

A cathode active material of the present invention comprises lithiumnickel manganese composite oxide particles having a layered hexagonalcrystal structure and expressed by the general formula ofLi_(1+u)Ni_(x)Mn_(y)Co_(z)M_(t)O₂ (where −0.05≤u≤0.50, x+y+z+t=1,0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, M is one or more added elementsthat are selected from among Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo and W),and the cathode active material has an average particle size of 2 to 8μm, a value [(d90−d10)/average particle size], which is an indexindicating an extent of particle size distribution thereof, of 0.60 orless, and the cathode active material has a hollow structure providedwith a hollow section inside the particles and an outer shell section ofaggregated sintered primary particles formed on the outside of thehollow section.

Preferably, a ratio of the thickness of the outer shell section withrespect to the particle size of the lithium nickel manganese compositeoxide particles is 5 to 45%.

Preferably, this cathode active material for a non-aqueous electrolytesecondary battery of the present invention is generated by themanufacturing method for a cathode active material of the presentinvention.

In the non-aqueous electrolyte secondary battery of the presentinvention, the cathode is formed using the cathode active material for anon-aqueous electrolyte secondary battery according to the presentinvention described above.

Effect of the Invention

With the present invention, nickel manganese composite hydroxideparticles are obtained that have a small and highly uniform particlesize, which can be used as raw material to manufacture lithium nickelmanganese composite oxide having a high specific surface area due tohollow structure thereof. Moreover, cathode active material comprisingthe lithium nickel manganese composite oxide can provide high capacity,good cycle characteristic and high output when used in a non-aqueouselectrolyte secondary battery, and a non-aqueous electrolyte secondarybattery that is formed using this cathode active material has excellentbattery characteristics.

The manufacturing methods for manufacturing the nickel manganesecomposite hydroxide particles and the cathode active material that areprovided by the present invention are simple and suitable forlarge-scale production, so the industrial value of the invention is verylarge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a process for manufacturing the nickelmanganese composite hydroxide of the present invention.

FIG. 2 is a flowchart of another process for manufacturing the nickelmanganese composite hydroxide of the present invention.

FIG. 3 is a flowchart of a process for manufacturing a lithium nickelmanganese composite oxide, which is a cathode active material, from thenickel manganese composite hydroxide of the present invention.

FIG. 4 is a flowchart of the flow from manufacturing the nickelmanganese composite hydroxide to manufacturing a non-aqueous electrolytesecondary battery.

FIG. 5 is an SEM photograph of the nickel manganese composite hydroxideof the present invention (with 1,000 magnification).

FIG. 6 is an SEM photograph of a cross section of the nickel manganesecomposite hydroxide of the present invention (with 10,000magnification).

FIG. 7 is an SEM photograph of the lithium nickel manganese compositeoxide, which is a cathode active material, of the present invention(with 1,000 magnification).

FIG. 8 is an SEM photograph of a cross section of the lithium nickelmanganese composite oxide, which is a cathode active material, of thepresent invention (with 10,000 magnification).

FIG. 9 is a cross-sectional view of a coin-type battery that was usedfor battery evaluation.

FIG. 10 is a drawing for describing an outline of an equivalent circuitthat was used for measurement and analysis in impedance evaluation.

MODE FOR CARRYING OUT THE INVENTION

The present invention relates to (1) nickel manganese compositehydroxide particles, which are the raw material for a cathode activematerial for a non-aqueous electrolyte secondary battery and themanufacturing method thereof, (2) a cathode active material for anon-aqueous electrolyte secondary battery that is obtained by using thenickel manganese composite hydroxide as raw material and themanufacturing method thereof, and (3) a non-aqueous electrolytesecondary battery that is obtained by using the cathode active materialfor a non-aqueous electrolyte secondary battery for the cathode.

In order to improve the performance of a non-aqueous electrolytesecondary battery, the effect of a cathode active material for anon-aqueous electrolyte secondary battery that is used for the cathodeis large. In order to obtain a cathode active material for a non-aqueouselectrolyte secondary battery that can obtain excellent batteryperformance, the particle size, particle size distribution and thespecific surface area are important factors, and a cathode activematerial having a desired particle structure, and that has been adjustedto have a desired particle size and particle size distribution ispreferred. In order to obtain that kind of cathode active material, itis necessary to use a nickel manganese composite hydroxide as rawmaterial that has a desired particle structure as well as a desiredparticle size and particle size distribution.

The invention according to (1) to (3) above is described in detailbelow, however, first, the nickel manganese composite hydroxideparticles and manufacturing method thereof, which are the main featuresof the present invention, will be explained.

(1-1) Nickel Manganese Composite Hydroxide Particles

The nickel manganese composite hydroxide particles of the presentinvention are expressed by the general expression ofNi_(x)Mn_(y)Co_(z)M_(t)(OH)_(2+a) (where x+y+z+t=1, 0.3≤x≤0.8,0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, 0≤a≤0.5, and M is one or more additionalelements that are selected from among Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Moand W), and are constructed by spherical secondary particles that areformed from an aggregation of a plurality of plate shaped primaryparticles, and the secondary particles have an average particle size of3 to 7 μm, the index for indicating the spread of the particle sizedistribution [(d90−d10)/average particle size] is 0.55 or less, and havea center section comprising fine primary particles and an outer shellsection on the outside of the center section that comprises plate shapedprimary particles that are larger than the fine primary particles.

The composite hydroxide particles above are particularly suited as theraw material for the cathode active material having a hollow structureof the present invention, so in the following explanation it is presumedthat these composite hydroxide particles are used as the raw materialfor the cathode active material of the present invention.

(Particle Structure)

As illustrated in FIG. 5, the composite hydroxide particles of thepresent invention are spherical particles. More specifically, asillustrated in FIG. 6, a plurality of primary particles are aggregatedtogether to form spherical secondary particles, even more specifically,the particles comprise a structure wherein the interior of the particleshave a center section comprising fine primary particles, and an outershell section on the outside of the center section comprising a plateshaped primary particles that are larger than the fine primaryparticles. With this structure, in the sintering process for forming thelithium nickel manganese composite oxide, which is the cathode activematerial of the present invention, dispersion of lithium inside theparticles is performed sufficiently, so it is possible to obtain a goodcathode active material having a uniform distribution of lithium.

Here, the center section is a structure comprising a collection of fineprimary particles, so when compared with the outer shell section thatcomprises larger thick plate shaped primary particles, in the sinteringprocess above, a contraction of the center section due to sinteringstart from a lower temperature. Therefore, during calcination, sinteringproceeds from a low temperature, and the contraction proceeds to theouter shell side where progress of sintering is slow, so space occurs inthe center section. The center section is considered to be low density,and the contraction rate is also high, so a sufficiently large space isformed in the center section. As a result, the cathode active materialthat is obtained after calcination has a hollow structure.

Moreover, it is more preferable that the outer shell of secondaryparticles be formed with the plate shaped primary particles beingaggregated in random directions. By the plate shaped primary particlesbeing aggregated in random directions, nearly uniform gap occurs betweenthe primary particles, and when mixing and calcining the compositehydroxide particles with the lithium compound, the molten lithiumcompound moves inside the secondary particles, and dispersion of thelithium is adequately performed.

Furthermore, by aggregating those particles in random directions,contraction of the particles of the center section during thecalcination process occurs evenly, so it is possible to form spaces ofsuitable size inside the cathode active material, which is preferred.

In order to form space during the calcination process, preferably theaverage particle size of the fine primary particles is 0.01 to 0.3 μm,and more preferably is 0.1 to 0.3 μm. Moreover, preferably the averageparticle size of the plate shaped primary particles, which are largerthan the fine primary particles, is 0.3 to 3 μm, and more preferably is0.4 to 1.5 μm, and particularly, even more preferably is 0.4 to 1.0 μm.When the average particle size of the fine primary particles is lessthan 0.01 μm, a center section having a sufficient size may not beformed in the composite hydroxide particles, and when the averageparticle size is greater then 0.3 μm, the lower temperature at the startof sintering and contraction of the center section are not sufficient,so it is possible that a space of adequate size will not be obtainedafter calcination. On the other hand, when the average particle size ofthe plate shaped particles of the outer shell section is less than 0.3μm, sintering is performed at low temperature during calcination, and itmay not be possible to obtain space having an sufficient size, and whengreater than 3 μm, in order for the crystallinity of the obtainedcathode active material to be suitable, it is necessary to increase thecalcination temperature, so sintering will occur between the secondaryparticles and the particle size of the obtained cathode active materialwill exceed the range above.

Furthermore, preferably the fine primary particles are plate shapedand/or needle shaped. By the fine primary particles having these shapes,the density of the center section is sufficiently low, contractionoccurs due to calcination, and a sufficient amount of space is created.

Moreover, in the case of the secondary particles above, preferably thethickness of the outer shell section is 5 to 45% the particle size ofthe secondary particles, and more preferably 7 to 35%. The cathodeactive material that is obtained with the composite hydroxide above asthe raw material has hollow structure, and the ratio of the thickness ofthe outer shell section with respect to the particle size is maintainedat that ratio for the composite hydroxide secondary particles above.Therefore, by keeping the ratio of the thickness of the outer shellsection with respect to the size of the secondary particles within therange above, it is possible to form a sufficient hollow section in thelithium nickel manganese composite oxide particles. When the thicknessof the outer shell section is so thin that the ratio with respect to theparticle size of the secondary particles is less than 5%, thecontraction of the composite hydroxide particles in the calcinationprocess when manufacturing the cathode active material becomes large,and sintering occurs between the secondary particles of the lithiumnickel manganese composite oxide, so there is a possibility that theparticle size distribution of the cathode active material will becomepoor. On the other hand, when the ratio exceeds 45%, problems such asnot being able to form a sufficiently large center section may occur.

The particle size of the fine primary particles and the plate shapedprimary particles, and the ratio of the thickness of the outer shellsection with respect to the particle size of the secondary particles canbe measured by using a scanning electron microscope to observe the crosssection of the nickel manganese composite hydroxide particles.

For example, a plurality of nickel manganese composite hydroxideparticles (secondary particles) can be embedded in resin or the like,and through cross-section polisher processing or the like, can be putinto a state such that the cross section can be observed. The particlesize of the fine primary particles and the plate shaped primaryparticles can be found by measuring as the maximum diameter of the crosssection of preferably 10 or more of the primary particles in thesecondary particle and calculating the average.

Moreover, the ratio of the thickness of the outer shell section withrespect to the particle size of the secondary particles can be found asdescribed below. From among the secondary particles in the resin above,particles in the center whose cross section can be observed areselected, and at three or more arbitrary locations, the distance betweentwo points where the distance from the outer surface of the outer shellsection to the inner surface on the center section side is the shortestis measured, and the average thickness of the outer shell section foreach particle is found. By taking the distance between two arbitrarypoints on the outer surface of the secondary particle to be the particlesize of the secondary particle, and dividing the average thickness bythe particle size of the secondary particle, the ratio of the thicknessof the outer shell section with respect to the particle size is foundfor each particle. Furthermore, by averaging the ratios that were foundfor 10 or more particles, it is possible to find the ratio of thethickness of the outer shell section with respect to the particle sizeof the secondary particles for the nickel manganese composite hydroxideparticles above.

(Average Particle Size)

The average particle size of the composite hydroxide particles of thepresent invention is adjusted to be 3 to 7 μm, and preferably 3.5 to 6.5μm. By making the average particle size 3 to 7 μm, the cathode activematerial that is obtained using the composite hydroxide particles of thepresent invention as raw material can be adjusted to have a specifiedaverage particle size (2 to 8 μm). The particle size of the compositehydroxide particles is correlated with the particles size of the cathodeactive material that is obtained, so affects the characteristics of abattery that uses this cathode active material as the cathode material.

More specifically, when the average particle size of the compositehydroxide particles is less than 3 μm, the average particle size of theobtained cathode active material also becomes small, and the packingdensity of the cathode decreases, and the battery capacity per volumedecreases. On the other hand, when the average particle size of thecomposite hydroxide particles exceeds 7 μm, specific surface area of thecathode active material decreases, and by reducing the interface betweenthe cathode active material and electrolyte the cathode resistanceincreases, and the output characteristics of the battery decreases.

(Particle Size Distribution)

The composite hydroxide particles of the present invention are adjustedso that the index [(d90−d10)/average particle size)] that indicates theextent of the particle size distribution is 0.55 or less, and preferably0.52 or less.

The particle size distribution of the cathode active material is greatlyaffected by the composite hydroxide particles, which are the rawmaterial, so when fine particles or coarse particles are mixed with thecomposited hydroxide particles, similar particles also exist in thecathode active material. In other words, when [(d90−d10)/averageparticle size)] exceeds 0.55 and the extent of the particle sizedistribution is large, fine particles or coarse particles also exist inthe cathode active material.

When the cathode is formed using cathode active material in which thereare many fine particles, there is a possibility that heat will begenerated due to localized reaction of the fine particles, and togetherwith a decrease in the safety of the battery, the fine particlesselectively deteriorate, so the cyclability of the battery becomes poor.On the other hand, when the cathode is formed using cathode activematerial in which there are many large particles, there is notsufficient reaction area between the electrolyte and the cathode activematerial, and the output of the battery decreases due to an increase inthe reaction resistance.

Therefore, the composite hydroxide particles of the present inventionare adjusted so that [(d90−d10)/average particle size] is 0.55 or less,and the range of particle size distribution of the cathode activematerial that is obtained by using these composite hydroxide particlesas raw material becomes small, so it is possible to make the particlesize uniform. In other words, the particle size distribution of cathodeactive material can be adjusted such that [(d90−d10)/average particlesize] is 0.60 or less. As a result, in a battery in which cathode activematerial that is formed using the composite hydroxide particles of thepresent invention is used as the cathode material, it is possible toachieve good cyclability and high output.

In the index [(d90−d10)/average particle size] that indicates the extentof the particles size distribution, d10 is the particle size when thenumber of particles of each particle size from the side of smallparticle size is cumulatively totaled, and that accumulated volume is10% of the total volume of all particles. Moreover, d90 is the particlesize when the number of particles is similarly totaled, and thataccumulated volume is 90% the total volume of all particles.

The method for finding the average particle size, d90 and d10 is notparticularly limited, however, for example, they can be found from thevolume integrated value that is measured using a laser diffractionscattering particle size analyzer. When d50 is used as the averageparticle size, it is possible to use the particle size when, as in thecase of d90, the accumulated volume is 50% the entire particle volume.

(Particle Composition)

The composite hydroxide particles of the present invention are adjustedso that the composition is expressed by the following general formula.By manufacturing a lithium nickel manganese composite oxide with anickel manganese composite hydroxide having the this composition as theraw material, and when using an electrode having that lithium nickelmanganese composite oxide as the cathode active material in a battery,not only is it possible to lower the value of the measured cathoderesistance, but it is also possible to improve the battery performance.Ni_(x)Mn_(y)Co_(z)M_(t)(OH)_(2+a)  General Formula:

(x+y+z+t=1, 0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, 0≤a≤0.5, M is oneor more additional elements that are selected from among Mg, Ca, Al, Ti,V Cr, Zr, Nb, Mo and W.)

When cathode active material with composite hydroxide particles as theraw material is obtained, the composition ratio (Ni:Mn:Co:M) of thecomposite hydroxide particles is maintained in the obtained cathodeactive material. Therefore, the composition ratio of the compositehydroxide particles of the present invention is adjusted so as to be thesame as the composition ratio that is required for the cathode activematerial to be obtained.

(1-2) Method for Manufacturing Nickel Manganese Composite HydroxideParticles

The method for manufacturing the composite hydroxide particles of thepresent invention is a method for manufacturing nickel manganesecomposite hydroxide particles by reaction crystallization, andcomprises: a) a nucleation step for performing nucleation, and b) aparticle growth step that grows the nuclei that were created in thenucleation process.

In other words, in the conventional continuous crystallization method,the nucleation reaction and the particle growth reaction proceededsimultaneously in the same tank, so the particle size distribution ofthe obtained composite hydroxide particles was over a wide range. On theother hand, a feature of the manufacturing method for the compositehydroxide particles of the present invention is that, by clearlyseparating the time when nucleation reaction occurs (nucleation step)and the time when the particle growth reaction occurs (particle growthstep), a narrow particle size distribution is achieved for the obtainedcomposite hydroxide particles. In addition, another feature of themanufacturing method of the present invention is that, by controllingthe atmosphere during the crystallization reaction, the particlestructure of the obtained complex hydroxide particles has a centersection composed of fine primary particles, and an outer shell sectionthat is composed of primary particles that are larger that in the centersection.

First, a summary of the method for manufacturing the composite hydroxideparticles of the present invention will be explained based on FIG. 1. InFIG. 1 and FIG. 2, (A) corresponds to the nucleation step and (B)corresponds to the particle growth step.

(Nucleation Step)

As illustrated in FIG. 1, first, a plurality of metallic compoundscontaining nickel and manganese are dissolved in water at specifiedratios, to make the mixed aqueous solution. In the method formanufacturing the composite hydroxide particles of the presentinvention, the composition ratio of the metal in the obtained compositehydroxide particles is the same as the composition ratio of the metalsin the mixed aqueous solution.

Therefore, the mixed aqueous solution is made by adjusting the ratio ofthe metal compounds to be dissolved in water, mainly nickel, manganeseand cobalt, so that the composition ratio of the metals in the mixedaqueous solution is the same composition ratio as the metals in thecomposite hydroxide particles of the present invention.

On the other hand, alkali aqueous solution such as sodium hydroxideaqueous solution, ammonia aqueous solution that includes an ammonium iondonor, and water are supplied to the reaction tank and mixed to form anaqueous solution. This aqueous solution (hereafter, referred to as the“aqueous solution before reaction”) is adjusted so that the pH value iswithin the range 12.0 to 14.0, and preferably within the range 12.3 to13.5 and even more preferably within the range 12.5 to 13.0 at astandard solution temperature of 25° C. by adjusting the amount ofalkali aqueous solution that is supplied. Moreover, the aqueous solutionis adjusted so that the concentration of ammonium ion in the aqueoussolution before reaction is 3 to 25 g/L, and preferably 5 to 20 g/L byadjusting the amount of ammonia aqueous solution that is supplied. Thetemperature of the aqueous solution before reaction is also preferablyadjusted to be 20° C. or greater, and more preferably to be within therange 20 to 60° C. The pH value of the aqueous solution in the reactiontank can be measured using a typical pH meter, and the ammonium ionconcentration can be measured with an ion meter.

In the reaction tank, after the temperature and pH of the aqueoussolution before reaction have been adjusted, the mixed aqueous solutionis supplied to the reaction tank while mixing with the aqueous solutionbefore reaction. As a result, the aqueous solution before reaction ismixed with the mixed aqueous solution, and an aqueous solution fornucleation, which is the reaction solution for the nucleation step isformed, and minute nuclei of composite hydroxide are formed in theaqueous solution for nucleation. At this time, the temperature and pH ofthe aqueous solution for nucleation are within the range above, so theformed nuclei do not grow much, and nucleation occurs with priority.

The pH value and the ammonium ion concentration of the aqueous solutionfor nucleation changes during formation of the nuclei due to the supplyof mixed aqueous solution, so alkali aqueous solution and ammoniaaqueous solution are supplied together with mixed aqueous solution tothe aqueous solution for nucleation, and the pH of the aqueous solutionfor nucleation is controlled so that the pH value at a standard solutiontemperature of 25° C. is kept within the range 12.0 to 14.0, and theammonium ion concentration is controlled to be within the range 3 to 25g/L.

By supplying the mixed aqueous solution, alkali aqueous solution andammonia aqueous solution to the aqueous solution for nucleation, newnuclei are continuously generated in the aqueous solution fornucleation. After a specified number of nuclei are generated in theaqueous solution for nucleation, the nucleation step ends. Whether ornot the specified number of nuclei has been generated is determinedaccording to the amount of metal salt added to the aqueous solution fornucleation.

(Particle Growth Step)

After the nucleation step has finished, the pH of the aqueous solutionfor nucleation at a standard solution temperature of 25° C. ispreferably adjusted to 10.5 to 12.0, and more preferably, to 11.0 to12.0, so that pH value is lower than the pH value during the nucleationstep, and an aqueous solution for particle growth, which is the reactionaqueous solution for the particle growth step, is obtained. Morespecifically, controlling the pH during this adjustment is performed byadjusting the amount of alkali aqueous solution that is supplied.

By keeping the pH value of the aqueous solution for particle growthwithin the range above, the growth reaction of the nuclei occurs withpriority over the formation reaction of nuclei, so in the particlegrowth step, hardly any new nuclei are formed in the aqueous solutionfor particle growth, and the nuclei are grown (particle growth) andcomposite hydroxide particle having a specified particle size areformed.

Similarly, as particles are grown by supplying mixed aqueous solution,the pH value and ammonium ion concentration of the aqueous solution forparticle growth changes, so the pH value of the aqueous solution forparticle growth is controlled by supplying alkali aqueous solution andammonia aqueous solution together with mixed aqueous solution to theaqueous solution for particle growth so that the pH value is kept withinthe range 1.05 to 12.0 at a standard solution temperature of 25° C., andthe ammonium ion concentration is kept within the range 3 to 25 g/L.

After that, at the instant when the composite hydroxide particles havegrown to a specified particle size, the particle growth step ends. Theparticle size of the composite hydroxide particles can be determinedeasily from preliminary testing from the amount of metal salt added tothe reaction solutions in both the nucleation step and particle growthstep, and when finding the relationship with the obtained particles,from the amount of metal salt added in each step.

As described above, in the case of the method for manufacturingcomposite hydroxide particles above, formation of nuclei takesprecedence in the nucleation step with hardly any nucleus growthoccurring, however, in the particle growth step only nucleus growthoccurs, and hardly any new nuclei are formed. Therefore, in thenucleation step it is possible to form homogeneous nuclei having anarrow particle size distribution range, and in the particle growthprocess, it is possible to homogeneously grow nuclei. Consequently, inthe method for manufacturing composite hydroxide particles, it ispossible to obtain homogeneous nickel manganese composite hydroxideparticles having a narrow particle size distribution range.

In the case of the manufacturing method above, in both steps, metallicions become nuclei or crystallize out as composite hydroxide particles,so the ratio of the liquid component to the metallic component in thereaction solutions increases. In that case, apparently, the density ofthe mixed aqueous solution that is supplied is decreased, andparticularly in the particle growth step, there is a possibility thatcomposite hydroxide particles will not grow sufficiently.

Therefore, preferably, in order to suppress the increase of liquidcomponent, part of the liquid component in the aqueous solution forparticle growth is drained to outside the reaction tank after thenucleation step ends and during the particle growth step. Morespecifically, the supply of mixed aqueous solution, alkali aqueoussolution and ammonia aqueous solution to the aqueous solution forparticle growth and mixing is stopped, the nuclei and compositehydroxide particles are caused to precipitate out, and the supernatantliquid of the aqueous solution for particle growth is drained out. As aresult, it is possible to increase the relative concentration of mixedaqueous solution in the aqueous solution for particle growth. Then, withthe relative concentration of the mix aqueous solution high, it ispossible to grow composite hydroxide particles, so it is possible tomake the particle size distribution of the composite hydroxide particleseven narrower, and thus it is also possible to increase the density ofthe composite hydroxide particles as secondary particles.

Moreover, in the embodiment illustrated in FIG. 1, after the nucleationstep ends, an aqueous solution for particle growth is formed byadjusting the pH of the aqueous solution for nucleation, and thenparticle growth step is performed after the nucleation step, so there isan advantage in that it is possible to quickly change to the particlegrowth step. Furthermore, there is the advantage that changing from thenucleation step to the particle growth step can be performed easily bysimply adjusting the pH of the reaction solution, and adjusting the pHcan also be performed easily by temporarily stopping the supply ofalkali aqueous solution. The pH of the reaction solution can also beadjusted by adding an inorganic acid that is the same kind as the acidof the metallic compounds into the reaction solution, for example,sulfuric acid is added in case of using sulfate as the metalliccompounds.

However, in another embodiment as illustrated in FIG. 2, separate fromthe aqueous solution for nucleation, a component adjustment solutionwhose pH and ammonium on concentration are adjusted to correspond to theparticle growth step is formed, and a solution containing the nucleithat were formed in the nucleation step in a separate tank (aqueoussolution for nucleation, and preferably, the aqueous solution from whichpart of liquid component has been removed) is added to this componentadjustment solution to form a reaction solution, and the particle growthstep can be performed with this reaction solution as the aqueoussolution for particle growth.

In this case, it is possible to separate the nucleation step andparticle growth step more completely, so the state of the reactionsolution in each step can be taken to be an optimum condition for thestep. Particularly, at the time when the particle growth step starts,the pH of the aqueous solution for particle growth can be taken to bethe optimum condition. Therefore, the range of the particle sizedistribution of the nickel manganese composite hydroxide particles thatare formed in the particle formation step can be narrower and morehomogeneous.

(Reaction Atmosphere)

Next, control of the reaction atmosphere in each step, the material andsolutions used in each step, and the reaction conditions will beexplained in detail.

The particle structure of the nickel manganese composite hydroxideparticles of the present invention is formed by controlling theatmosphere in the reaction tank during the nucleation step and particlegrowth step. Therefore, controlling the atmosphere in each of the stepsof the manufacturing method has important significance. Growth of theprimary particles that form the nickel manganese composite hydroxideparticles is controlled according to the atmosphere in the reaction tankduring the crystallization reaction, and in an oxidizing atmosphere,low-density particles having many gaps are formed from the fine primaryparticles, and in a weak oxidizing atmosphere to a non-oxidizingatmosphere, minute high-density particles with large primary particlesare formed.

In other words, by using an oxidizing atmosphere for the nucleation stepand part of the initial particle growth step, a center section composedof fine primary particles is formed, and in the particle growth stepafter that, by switching from the oxidizing atmosphere to an atmospherewithin a range of from a low-oxidizing atmosphere to a non-oxidizingatmosphere, it is possible to for the particle structure above having anouter shell section composed of plate shaped primary particles that arelarger than the fine primary particles of the center section.

In the crystallization reaction in which the atmosphere is controlled,normally, the primary particles in the center section are fine plate orneedle shaped, and the primary particles of the outer shell section areplate shaped. However, the primary particles of the nickel manganesecomposite hydroxide above, depending on the composition, may also berectangular, elliptical, trigonal or the like.

The oxidizing atmosphere for forming the center section described aboveof the present invention is defined as being an atmosphere wherein theoxygen concentration in the reaction tank space is greater than 1% byvolume. An oxidizing atmosphere wherein the oxygen concentration isgreater than 2% by volume is preferred, and an oxidizing atmospherewherein the oxygen concentration is greater than 10% by volume is evenmore preferred; where an air atmosphere (oxygen concentration: 21% byvolume) that is easily controlled is particularly preferred. By using anatmosphere wherein the oxygen concentration is greater than 1% byvolume, it is possible to make the average particle size of the primaryparticles 0.01 to 0.3 μm. When the oxygen concentration is equal to orless than 1% by volume, the average particle size of the primaryparticles in the center section may exceed 0.3 μm. The upper limit ofthe oxygen concentration is not particularly limited, however, when theoxygen concentration exceeds 30% by volume, the average particle size ofthe primary particles may become less than 0.01 μm, which is notpreferred.

On the other hand, the atmosphere in the range of from a weak oxidizingatmosphere to a non-oxidizing atmosphere for forming the outer shelldescribed above of the present invention is defined by an atmospherewherein the oxygen concentration of the space inside the reaction tankis 1% by volume or less. So that the oxygen concentration is preferably0.5% by volume or less, and even more preferably, 0.2% by volume orless, the atmosphere is controlled to be a mixed atmosphere of oxygenand inert gasses. By making the oxygen concentration of the space insidethe reaction tank 1% by volume or less and causing particles to grow, itis possible to suppress unnecessary oxidation of particles, promotegrowth of primary particles, and obtain secondary particles having ahigh-density shell section with uniform primary particles having anaverage particle size of 0.3 to 3 μm and larger than in the centersection. As a method for keeping the space inside the reaction tank inthis kind of atmosphere, there is a method of causing inert gas such asnitrogen to flow to the space inside the reaction tank, and furthercausing bubbling of inert gas in the reaction solution.

The timing for switching the atmosphere in the particle growth step isset by taking into consideration the size of the center section of thenickel manganese composite hydroxide particles so that a center sectionis obtained wherein cyclability does not become bad due to theoccurrence of fine particles in the finally obtained cathode activematerial. For example, the switching is performed in a range of 0 to 40%of the time from the start of the particle growth process with respectto the entire particle growth processing time, and preferably, in therange of 0 to 30% of the time, and even more preferably, in a range of 0to 25% of the time. When switching is performed at a point in time thatexceeds 40% of the overall particle growth processing time, the formedcenter section becomes large, and the thickness of the outer shellsection with respect to the particle size of the secondary particlesbecomes too thin. On the other hand, when switching is performed beforethe particle growth process, or in other words, performed during thenucleation process, the center section becomes too small, and secondaryparticles having the structure above are not formed.

(pH Control)

As described above, in the nucleation step, the pH value of the reactionsolution must be controlled so that the pH value at a standard solutiontemperature of 25° C. is within the range 12.0 to 14.0, and preferably,within the range 12.3 to 13.5. When the pH value exceeds 14.0, thenuclei that are formed are too fine, and there is a problem that thereaction solution becomes a gel. Moreover, when the pH value is lessthan 12.0, the nucleus growth reaction occurs together with nucleation,so the range of the particle size distribution of the formed nucleibecomes large, and heterogeneous. In other words, in the nucleationstep, by controlling the pH value of the reaction solution within therange above, it is possible to suppress nucleus growth, and promote onlynucleation, and the formed nuclei are homogeneous and the particle sizedistribution range can be kept narrow.

On the other hand, in the particle growth step, the pH value of thereaction solution must be controlled so that the pH value at a standardsolution temperature of 25° C. is within the range 10.5 to 12.0, andpreferably, within the range 11.0 to 12.0. When the pH value exceeds12.0, the amount of newly formed nuclei increases, and fine secondaryparticles are formed, so hydroxide particles having a good particle sizedistribution cannot be obtained. Moreover, when the pH value is lessthan 10.5, the solubility due to ammonium ions is high, and the amountof metal ions that remain in the solution without precipitating outincreases, so production efficiency becomes poor. In other words, in theparticle growth step, by controlling the pH of the reaction solutionwithin the range above, it is possible to cause only growth of thenuclei formed in the nucleation step to occur and suppress the formationof new nuclei, and thus the obtained nickel manganese compositehydroxide particles are homogeneous and the particle size distributionrange can be kept narrow.

In both the nucleation step and the particle growth step, preferably therange of fluctuation of the pH is kept within the set value ±0.2. Whenthe range of fluctuation of the pH is large, nucleation and particlegrowth do not become fixed, and there is a possibility that uniformmanganese composite hydroxide particles having a narrow particle sizedistribution range will not be obtained.

When the pH value is 12.0, this pH value is the boundary conditionbetween nucleation and nucleus growth, so, depending on whether or notthere are nuclei in the reaction solution, this pH value will become thecondition for the nucleation step or the particle growth step.

In other words, after the pH value for the nucleation step is made to begreater than 12 a large quantity of nuclei are formed, then when the pHvalue for the particle growth step is made to be 12, there is a largequantity of nuclei in the reaction solution, so nucleus growth occurswith priority, and hydroxide particles have a narrow particle sizedistribution and relative large particle size are obtained.

On the other hand, when there are no nuclei in the reaction solution, orin other words, when the pH value during the nucleation step is 12,there are no nuclei that have grown, so the formation of nuclei takesprecedence, and by lowering the pH value of the particle growth step tobe less than 12, the nuclei that are formed grow and good hydroxideparticles are obtained.

In either case, the pH value of the particle growth step should becontrolled to be a value that is less than the pH value in thenucleation step, and in order to clearly separate nucleation fromparticle growth, the pH value of the particle growth step is preferablyat least 0.5 less than the pH value of the nucleation step, and evenmore preferably at least 1.0 less.

(Nucleation Amount)

The amount of nuclei formed during the nucleation step is notparticularly limited, however, in order to obtain composite hydroxideparticles having good particle size distribution, preferably the amountis 0.1% to 2% of the total volume, or in other words the amount of allmetal salts supplied to obtain the composite hydroxide particles, andmore preferably 1.5% or less.

(Controlling the Particle Size of Composite Hydroxide Particles)

The particle size of the composite hydroxide particles above can becontrolled by the time of the particle growth step, so by continuing theparticle growth step until the particles have been grown to a desiredparticle size, it is possible to obtain composite hydroxide particleshaving a desired particle size.

Moreover, the particle size of the composite hydroxide particles can becontrolled not only by the particle growth step, but also by the pHvalue of the nucleation step and the amount of raw material added fornucleation.

In other words, by making the pH value during nucleation the high pHvalue side, or by increasing the amount of raw material added byincreasing the nucleation time, number of nuclei formed is increased. Asa result, even when the particle growth conditions are kept the same, itis possible to make the particle size of the composite hydroxideparticles small.

On the other hand, by performing control to reduce the number of nucleiformed, it is possible to increase the particle size of the obtainedcomposite hydroxide particles.

In the following, the conditions for the metallic compounds, ammoniaconcentration in the reaction aqueous solution, reaction temperature andthe like are explained, however, the difference between the nucleationstep and the particle growth step is just the range for controlling thepH of the reaction aqueous solution and the atmosphere inside thereaction tank, with the conditions such as the metallic compounds,ammonia concentration in the reaction aqueous solution, reactiontemperature and the like essentially being the same in both steps.

(Metal Compounds)

As metal compounds, compounds containing the target metals are used. Thecompounds used are preferably compounds that are water soluble such asnitrates, sulfates and hydrochlorides. For example, nickel sulfate,manganese sulfate and cobalt sulfate are preferably used.

(Added Elements)

Preferably compounds that are water soluble are used as the sources ofthe added elements (one or more elements that are selected from amongMg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo and W); for example, titanium sulfate,ammonium peroxotitanic, titanium potassium oxalate, vanadium sulfate,ammonium vanadate, chromium sulfate, potassium chromate, zirconiumsulfate, niobium oxalate, ammonium molybdate, sodium tungstate, ammoniumtungstate, and the like can be used.

When uniformly dispersing the added elements inside the compositehydroxide particles, it is only necessary to precipitate out the addedelements into the composite hydroxide particles in a uniformly dispersedstate by adding additives that contain the added elements to the mixedsolution.

Moreover, when coating the surface of the composite hydroxide particleswith the added elements, for example, by forming a slurry of compositehydroxide particles in an aqueous solution that includes the addedelements, and performing control so that the pH becomes a specifiedvalue, then adding an aqueous solution that includes the one or moreadded elements and depositing the added elements onto the surface of thecomposite hydroxide particle by reaction crystallization, it is possibleto uniformly cover the surface with the added elements. In this case, itis also possible to use an alkoxide solution of the added elementsinstead of an aqueous solution containing the added elements.Furthermore, it is also possible to coat the surface of the compositehydroxide particles with the added elements by spraying an aqueoussolution or slurry containing the added elements on the compositehydroxide particles, and drying out the coated particles. Moreover, thesurface can be coated by a method of spraying and drying slurry in whichthe composite hydroxide particles and salt including the one or moreadded elements are suspended, or mixing a composite hydroxide and saltcontaining the one or more added elements using a solid-phase method.

When coating the surface with added elements, by reducing the atomicratios of the added element that exist in the mixed solution by just theamount of coating, it is possible to match the atomic ratios with theatomic ratios of the metal ions of the obtained composite hydroxideparticles. The step of coating the surface of the particles with addedelements can also be performed for the particles after the compositehydroxide particles have been heated.

(Mixed Solution Concentration)

Preferably, the concentration of the mixed solution is 1 to 2.6 mol/Lfor the total metallic compounds, and preferably 1.5 to 2.2 mol/L. Whenthe concentration of the mixed solution is less than 1 mol/L, the amountof crystallization per reaction tank decreases, so productivitydecrease, which is not preferable.

On the other hand, when the salt concentration of the mixed solutionexceeds 2.6 mol/L, the concentration exceeds the saturated concentrationat normal temperature, so crystals are reprecipitated and there is adanger that piping of the equipment will become blocked.

Moreover, the metallic compounds do not need to be supplied to thereaction tank as a mixed solution, and, for example, when using metalliccompounds that are formed by reacting when mixed, separate metalliccompound solutions can be prepared and the individual solutions ofmetallic compounds can be supplied at the same time to the reaction tankso that total concentration of metallic compound solution is within therange above.

Furthermore, that amount of mixed solution or amount of individualmetallic compound solutions that are supplied to the reaction tankshould be such that the concentration of crystallization at the timethat the crystallization reaction ends is roughly 30 to 200 g/L, andpreferably 80 to 150 g/L. When the concentration of crystallizedmaterial is less than 30 g/L, there is insufficient aggregation ofprimary particles, and when the concentration exceeds 200 g/L, the mixedsolution that is added is not sufficiently dispersed inside the reactiontank, so there is a possibility that there will be deviation in particlegrowth.

(Ammonia Concentration)

The ammonia concentration in the reaction aqueous solution, in orderthat the following problems do not occur, is preferably kept at aconstant value within the range of 3 to 25 g/L, and more preferablywithin the range of 5 to 20 g/L.

Ammonia is used as a complexing agent, and when the ammoniaconcentration is less than 3 g/L, it is not possible to maintain thesolubility of metal ions constant, it is not possible to form plateshaped hydroxide primary particles having an orderly shape and particlesize, and gel shaped nuclei are easily generated so the particle sizedistribution also easily increases.

On the other hand, when the ammonia concentration exceeds 25 g/L, thesolubility of metal ions becomes too large, the amount of metal ionsremaining in the reaction aqueous solution increases, and compositionaldistortion occurs.

Moreover, when the ammonia concentration fluctuates, the metal ionsolubility fluctuates, and uniform hydroxide particles are not formed,so preferably the concentration is kept at a constant value. Forexample, preferably the ammonia concentration is kept at a desiredconcentration so that the difference between the upper limit and lowerlimit is 5 g/L.

The ammonium ion donor is not particularly limited, however, forexample, ammonia, ammonium sulfate, ammonium chloride, ammoniumcarbonate, ammonium fluoride or the like is used.

(Reaction Temperature)

Inside the reaction tank, the temperature of the reaction solution ispreferably 20° C. or greater, and particularly is set to preferably 20to 60° C. When the temperature of the reaction solution is less than 20°C., the solubility is low, so the generation of nuclei occurs easily andcontrol becomes difficult. On the other hand, when the temperature isgreater than 60° C., the volatilization of the ammonia is promoted, soin order to maintain a specific ammonia concentration, an extra amountof the ammonium ion donor must be added, so the cost increases.

(Alkali Aqueous Solution)

In regards to the alkali aqueous solution that is used to adjust the pHof the reaction solution, the solution is not particularly limited; forexample, it is possible to use an alkali metal hydroxide aqueoussolution such as sodium hydroxide, potassium hydroxide and the like. Inthe case of alkali metal hydroxide, it is possible to supply that alkalimetal hydroxide directly to the reaction solution, however, from theaspect of ease of control the pH of the reaction solution in thereaction tank, adding the alkali metal hydroxide to the reactionsolution in the reaction tank as an aqueous solution thereof ispreferred.

Moreover, the method for adding the alkali aqueous solution to thereaction tank is also not particularly limited, and can be added using apump capable of flow control, such as a constant rate pump, whilesufficiently mixing the reaction solution so that the pH value of thereaction solution is kept within the specified range.

(Manufacturing Equipment)

In the method for manufacturing composite hydroxide particles of thepresent invention, an apparatus is used that does not collect theproduced material until the reaction is complete. For example, theapparatus is a typically used batch reaction tank in which a mixer isprovided. When using this kind of apparatus, a problem of collectinggrowing particles at the same time as the overflow liquid, such asoccurs in a continuous crystallization apparatus that collects theproduced material by a typical overflow, does not occur, so it ispossible to obtain particles having a narrow particle size distributionand uniform particle size.

Moreover, it is necessary to control the reaction atmosphere, so usingan apparatus, such as a sealed apparatus, that is capable of atmospherecontrol is preferred. By using such an apparatus, it is possible tomanufacture composite hydroxide particles having the structure above,and it is possible to uniformly promote the nucleation reaction andparticle growth reaction, so it is possible to obtain particles having agood particle size distribution, or in other words, particles having anarrow particle size distribution range.

(2-1) Cathode Active Material for a Non-Aqueous Electrolyte SecondaryBattery

The cathode active material of the present invention is lithium nickelmanganese composite oxide particles that are represented by the generalformula of Li_(1+u)Ni_(x)Mn_(y)Co_(z)M_(t)O₂ (where −0.05≤u≤0.50),x+y+z+t=1, 0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, and M is one or moreadded elements that are selected from among Mg, Ca, Al, Ti, V, Cr, Zr,Nb, Mo and W), and has a layered hexagonal crystal structure.

(Composition)

The cathode active material of the present invention is lithium nickelmanganese composite oxide particles, and the composition thereof isadjusted so as to satisfy the following general formula.Li_(1+u)Ni_(x)Mn_(y)Co_(z)M_(t)O₂  General formula:

(where −0.05≤u≤0.50), x+y+z+t=1, 0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4,0≤t≤0.1, and M is one or more added elements that are selected fromamong Mg, Ca, Ti, V, Cr, Zr, Mo and W).

In the cathode active material of the present invention, u, whichindicates the surplus amount of lithium, is within the range −0.5 to0.50. When the surplus amount of lithium is less than −0.05, thereaction resistance of the cathode of the non-aqueous electrolytesecondary battery that uses the obtained cathode active material becomeslarge, so the output of the battery becomes low. On the other hand, whenthe surplus amount of lithium exceeds 0.05, the initial dischargecapacity when the cathode active material above is used for the cathodeof the battery decreases, and the reaction resistance of the cathodealso increases. In order to further reduce the reaction resistance,preferably the surplus amount u of Lithium is 0.10 or greater and 0.35or less.

As expressed in the general formula above, the cathode active materialof the present invention is preferably adjusted so that the lithiumnickel manganese composite oxide particles contain added element(s) M.By containing element(s) M above, it is possible to improve thedurability, and output characteristics of a battery that uses thiscathode active material.

Particularly, by uniformly distributing the added element on the surfaceor inside the particles, it is possible to obtain the above effect ofall particles, and together with obtaining the effect above by adding asmall amount, it is possible to suppress a decrease in capacity.

Furthermore, in order to obtain the effect by adding an even smalleramount, preferably the concentration of added element on the surface ishigher than that inside the particles.

When the atomic ratio y of the added element(s) M with respect to allatoms exceeds 0.05, the metal elements that contribute to the Redoxreaction decrease, so the battery capacity decreases, which is notpreferred. Therefore, the added element(s) M is adjusted so that theatomic ratio y is within the range above.

(Average Particle Size)

As illustrated in FIG. 7, the cathode active material of the presentinvention has an average particle size of 2 to 8 μm. When the averageparticle size is less than 2 μm, the packing density of particles whenthe cathode is formed decreases, and the battery capacity per volume ofthe cathode decreases. On the other hand, if the average particle sizeexceeds 8 μm, the specific surface area of the cathode active materialdecreases lowering the interface between the cathode active material andthe electrolyte of the battery. As a result, the resistance of thecathode increases and the output characteristic of the batterydecreases.

Therefore, by adjusting the cathode active material so that the averageparticle size becomes 2 to 8 μm, preferably 3 to 8 μm, furtherpreferably 3 to 6.5 μm, it is possible to increase the battery capacityper volume of the battery that uses this cathode active material for thecathode, and it is possible to obtain excellent battery characteristicssuch as safety and high output.

(Particle Size Distribution)

As illustrated in FIG. 7, for the cathode active material compriseshighly homogeneous lithium nickel manganese composite oxide secondaryparticles having an index [(d90−d10)/average particle size] thatindicates the size of the particle size distribution of 0.60 or less andpreferably 0.55 or less.

When particle size distribution is wide, there are many fine particleshaving a particle size that is very small with respect to the averageparticle size, or coarse particles having a particle size that is verylarge with respect to the average particle size. When the cathode isformed using a cathode active material having many fine particles, thereis a possibility that heat will be generated due to localized reactionof the fine particles, and together with a decrease in safety, fineparticles selectively deteriorate, causing the cyclability to becomepoor. On the other hand, when the cathode is formed using cathode activematerial having many coarse particles, there is not sufficient reactionarea for the electrolyte and cathode active material, and thus thebattery output decreases due to an increase in reaction resistance.

Therefore, by making the index [(d90−d10)/average particle size]described above 0.60 or less with regard to the particle sizedistribution of the cathode active material, it is possible to reducethe ratio of fine particles or coarse particles in the cathode activematerial, and a battery that uses this cathode active material for thecathode is very safe, and has good cyclability and battery outputcharacteristics. The average particle size, d90 and d10 are the same asthose used for the composite hydroxide particles, and measurement isperformed in the same way.

(Particle Structure)

As illustrated in FIG. 8, a feature of the cathode active material ofthe present invention is the hollow structure comprising a hollowsection inside the secondary particles and an outer shell section on theoutside. By having this kind of hollow structure, it is possible toincrease the reaction area, and electrolyte enter inside from theparticle boundaries or gaps between the primary particles of the outershell section, and lithium is inserted and removed at the reactiveinterface on the surface of the primary particles on the hollow sectionside inside the particles as well, so mobility of Li ions and electronsis not hindered, and it is possible to increase the outputcharacteristic.

Here, preferably the ratio of the thickness of the outer shell sectionwith respect to the particle size of the lithium nickel manganesecomposite oxide particles is 5 to 45% and more preferably, 8 to 38%.Moreover, preferably the absolute value is within the range 0.5 to 2.5μm, and it is particularly preferred that the range be 0.4 to 2.0 μm.When the ratio of the thickness of the outer shell section with respectto the particle size is less than 5%, the strength of the lithium nickelmanganese composite oxide particles decreases, so handling the powder,and when used in a battery cathode, the particles break down and becomefine particles, making the characteristics poor. On the other hand, whenthe ratio of the thickness of the outer shell section with respect tothe particle size exceeds 45%, only a small amount of electrolyte entersinside the hollow section inside the particles from the particleboundaries and spaces, and the surface area that contributes to thebattery reaction becomes smaller, so the cathode resistance increasesand the output characteristic decreases. The ratio of the thickness ofthe outer shell section with respect to the lithium nickel manganesecomposite oxide particle size can be found in the same way as for thecomposite hydroxide particles.

(Characteristics)

When the cathode active material above is used for example in thecathode of a 2032 type coin battery, when cobalt is not added, highinitial discharge capacity of 200 mAh/g or greater is obtained, and evenwhen cobalt is added at an atomic ratio of 30% of the entire metallicelements other than lithium, a high initial discharge capacity of 150mAh/g is obtained, and low cathode resistance and high cycle capacityretention is obtained, which are excellent characteristics for a cathodeactive material for a non aqueous electrolyte secondary battery.

(2-2) Method for Manufacturing Cathode Active Material for a Non-AqueousElectrolyte Secondary Battery

As long as the method for manufacturing the cathode active material ofthe present invention is such that the cathode active material has theaverage particle size, particle size distribution and particle structureabove, the method is not particularly limited, however, by employing themethod below the cathode active material can surely be manufactured, sois preferred.

As illustrated in FIG. 3, the method for manufacturing cathode activematerial of the present invention includes: a) a step of heat treatingthe nickel manganese composite hydroxide particles that are the rawmaterial for the cathode active material of the present invention; b) amixing step for forming a mixture by mixing a lithium compound into theparticles after heat treatment; and c) a calcination step of calciningthe mixture that was formed in the mixing step. Each of the steps willbe explained below.

a) Heat Treatment Step

The heat treatment step is a step for performing heat treatment thatheats the nickel manganese composite hydroxide particles (hereafter,referred to as composite hydroxide particles) to a temperature of 105 to750° C. and removes the moisture contained in the composite hydroxideparticles. By performing this heat treatment step, moisture that remainsin the particles up to the calcination step can be reduced to a fixedamount. As a result, it is possible to prevent fluctuation in thepercentage of the number of metal atoms or the number of lithium atomsin the manufactured cathode active material.

Moisture should be removed to an amount such that fluctuation in thepercentage of the number of metal atoms or the number of lithium atomsin the manufactured cathode active material does not occur, so it is notabsolutely necessary to convert all of the composite hydroxide particlesto nickel manganese composite oxide particles (hereafter, referred to ascomposite oxide particles). However, in order to further reduce thefluctuation described above, preferably the heating temperature is 500°C. or greater, and all of the composite hydroxide particles areconverted to composite oxide particles.

In the heat treatment step, when the heating temperature is less the105° C., it is not possible to remove the surplus moisture in thecomposite hydroxide particles, and it is not possible to suppress thefluctuation above. On the other hand, when the heating temperatureexceeds 750° C., the particles are sintered by the heat treatment, andit is not possible to obtain composite oxide particles having a uniformparticle size. The metallic component that is included in the compositehydroxide particles is analyzed according to the heat treatmentconditions and found beforehand, and by determining a ratio with thelithium compound, it is also possible to suppress the fluctuation.

The atmosphere for performing heat treatment is not particularlylimited, and can be a non-reducing atmosphere, however, preferably heattreatment is performed in an airflow of normal atmosphere which can beperformed easily.

Moreover, the heat treatment time is not particularly limited, however,when the time is less than one hour, the removal of surplus moisture inthe composite hydroxide particles cannot be performed sufficiently, sopreferably the time is one hour or longer, and more preferably 5 to 15hours.

The equipment that is used in the heat treatment is not particularlylimited, and as the composite hydroxide particles can be heated in anon-reducing atmosphere, or preferably in an airflow of normalatmosphere, an electric furnace that does generate gas can suitably beused.

b) Mixing Step

The mixing step is a step for obtaining a lithium mixture by mixing thecomposite hydroxide particles that were heat treated in the heattreatment step (hereafter, referred to as heat treated particles) with amaterial containing lithium, for example a lithium compound.

Here, not only the composite hydroxide particles from which residualmoisture was removed in the heat treatment step, but also complex oxideparticles that were converted to oxides in the heat treatment step or amixture of these particles is contained in the heat treated particles.

The heat treated particles and the lithium compounds are mixed so thatthe ratio of the number of lithium atoms with respect to the number ofmetal atoms other than lithium in the lithium mixture, in other words,the sum of the atoms of nickel, manganese, cobalt and added elements(Me) (Li/Me) is 0.95 to 1.5, and preferably 1 to 1.5, and morepreferably 1.1 to 1.35. In other words, the ratio Li/Me does not changebefore and after the calcination step, so the ratio Li/Me in the mixingstep become the ratio Li/Me in the cathode active material, so mixing isperformed so that the ratio Li/Me of the lithium compound is the same asthe ratio Li/Me in the cathode active material to be obtained.

The lithium compound that is used for forming the lithium mixture is notparticularly limited, however, for example, from the aspect of the easeof obtaining material, lithium hydroxide, lithium sulfate, lithiumcarbonate or a mixture of these is preferred. Particularly taking intoconsideration the ease of handling and the stability of quality,preferably lithium hydroxide or lithium carbonate is used.

Preferably the lithium mixture is sufficiently mixed before calcination.When mixing is not sufficient, there is a possibility that problems willoccur such as fluctuation in Li/Me between individual particles, andsufficient battery characteristics will not be obtained.

Furthermore, a typical mixer can be used for mixing; for example, it ispossible to use a shaker mixer, Lödige mixer, Julia mixer, V blender orthe like, and the composite oxide particles should be sufficiently mixedwith material containing lithium to an extent that the framework of theheat treated particles is not broken down.

c) Calcination Step

The calcination step is a step that caclinates the lithium mixture thatwas obtained in the mixing step, and forms a lithium nickel manganesecomposite oxide. When the lithium compound is calcinated in thecalcination step, the lithium in a lithium containing material isdispersed in the heat treated particles, so a lithium nickel manganesecomposite oxide is formed.

(Calcination Temperature)

The calcination of the lithium mixture is preferably performed at atemperature of 800 to 980° C., and more preferably 820 to 960° C.

When the calcination temperature is less than 800° C. dispersion oflithium into the heat treated particles is not performed sufficiently,and surplus lithium or unreacted particles remain, the crystal structureis not sufficiently arranged, and when used in a battery, sufficientbattery characteristics are not obtained.

Moreover, when the calcination temperature exceeds 980° C., there is apossibility that together with severe sintering occurring betweencomposite oxide particles, there will be abnormal particle growth, sothere is a possibility that the particles after calcination will becomecoarse, and it will not be possible to maintain the particle shape(spherical particles shape to be described next). In the case of thiskind of cathode active material, the specific surface area decreases, sowhen used in a battery, there is a problem in that the cathoderesistance increases and the battery capacity decreases.

From the aspect of uniformly performing the reaction between the heattreated particles ad the lithium compound, preferably the temperatureabove will rise at a temperature increase rate of 3 to 10° C./min.Furthermore, by maintaining the temperature at near the melting point ofthe lithium compound for 1 to 5 hours, it is possible to perform an evenmore uniform reaction.

(Calcination Time)

Of the calcination time, the hold time, during which the temperature ismaintained at a specified temperature, is preferably at least 2 hours,and more preferably 4 to 24 hours. When the time is less than 2 hours,it is possible that the formation of the lithium nickel manganesecomposite oxide will not be performed sufficiently. After this hold timeis finished, the time is not particularly limited, however, when thelithium mixture is accumulated in a sagger and calcinated, in order toprevent deterioration of the sagger, preferably the atmosphere is cooledto 200° C. at a cooling rate of 2 to 10° C./min.

(Temporary Calcination)

Particularly, when lithium hydroxide or lithium carbonate is used as thelithium compound, temporary calcination is performed by maintaining thetemperature at a temperature of 350 to 800° C., which is lower than thecalcination temperature, and preferably at a temperature of 450 to 780°C. for 1 to 10 hours, and preferably 3 to 6 hours. In other words,preferably temporary calcination is performed at the reactiontemperature of the lithium hydroxide or lithium carbonate and the heattreated particles. In this case, by maintaining the temperature at nearthe reaction temperature of the lithium hydroxide or lithium carbonate,it is possible to sufficiently perform dispersion of the lithium intothe heat treated particles, and thus it is possible to obtain uniformlithium nickel manganese composite oxide.

When it is desired to increase the concentration of added element M onthe surface of the lithium nickel manganese composite oxide particles,heat treated particles of the raw material, the surface of which areuniformly coated by the added element M, can be used. By calcining alithium mixture that contains the heat treated particles under moderateconditions, is possible to increase the concentration of the addedelement M on the surface of the lithium nickel manganese composite oxideparticles. More specifically, by calcining a lithium mixture thatcontains heat treated particles coated by the added element M at atemperature lower than the calcination temperature and for a timeshorter than the calcination time, it is possible to obtain lithiumnickel manganese composite particles having an increased concentrationof added element M on the surface of the particles.

Even when a lithium mixture containing heat treated particles coatedwith the added element M calcinated, when the calcination temperature ishigh and the calcination time is long, it is possible to obtain lithiumnickel manganese composite oxide particles in which the added element isuniformly distributed inside the particles. In other words, by adjustingthe heat treated particles of the raw material and the calcinationconditions, it is possible to obtain lithium nickel manganese compositeoxide particles having the target concentration distribution.

(Calcination Atmosphere)

The calcination atmosphere is preferably an oxidizing atmosphere, andmore preferably the oxygen concentration is 18 to 100% by volume, and amixed atmosphere of oxygen having the oxygen concentration describedabove and an inert gas is particularly preferred. In other words,preferably calcination is performed in atmospheric air or in an oxygenflow. When the oxygen concentration is less than 18% by volume, there isa possibility that the crystallinity of the lithium nickel manganesecomposite oxide will not be sufficient. Particularly, when consideringthe battery characteristics, performing calcination in oxygen flow ispreferred.

The furnace that is used in calcination is not particularly limited, andas long as the lithium mixture can be heated in atmospheric air or inoxygen flow, any kind of furnace can be used, however, from the aspectof uniformly maintaining the atmosphere inside the furnace, an electricfurnace in which gas is not generated is preferred, and it is possibleto use either a batch type or continuous type of furnace.

(Cracking)

Of the lithium nickel manganese composite oxide particles obtained bycalcination, aggregation or light sintering may occur. In that case, theparticles must be cracked, and as a result, lithium nickel manganeseoxide, or in other words, the cathode active material of the presentinvention can be obtained. Cracking is an operation for loosening up anaggregate wherein mechanical energy is applied to an aggregate of aplurality of secondary particles resulting from sintering neckingbetween secondary particles during calcination in order to separate thesecondary particles without breaking down the secondary particlesthemselves.

(3) Non-Aqueous Electrolyte Secondary Battery

The non-aqueous electrolyte secondary battery of the present inventionemploys a cathode that uses the cathode active material for anon-aqueous electrolyte secondary battery for the cathode. First, theconstruction of the non-aqueous electrolyte secondary battery of thepresent invention will be explained.

Except for using cathode active material of the present invention, theconstruction of the non-aqueous electrolyte secondary battery of thepresent invention essentially comprises the same construction as atypical non-aqueous electrolyte secondary battery.

More specifically, the secondary battery of the present inventioncomprises a case, a cathode and anode that are housed in the case, anon-aqueous electrolyte as a separator. Even more specifically, anelectrode unit that is obtained by layering a cathode and anode with aseparator in between is impregnated with a non-aqueous electrolyte, andcollector leads are used to connect between the cathode currentcollector of the cathode and the cathode terminal that leads to theoutside, and between the anode current collector of the anode and theanode terminal that leads to the outside, and these are sealed in thecase to form the secondary battery of the present invention.

The construction of the secondary battery of the present invention,needless to say, is not limited to the example above, and various shapescan be used for the external shape such as a can shape, layered shape orthe like.

(Cathode)

First, the cathode, which is the feature of the secondary battery of thepresent invention, is explained. The cathode is a sheet shaped member,and is formed, for example, by coating and drying a cathode compoundpaste that contains the cathode active material of the present inventionon the surface of an aluminum foil collector.

The cathode is appropriately processed to correspond to the type ofbattery used. For example, processing such as a cutting process to forma suitable size for the battery, a compression process such as rollpressing or the like to increase the electrode density and the like isperformed.

The cathode compound paste is formed by adding a solvent to the cathodecompound and mixing. The cathode compound is a mixing the powder cathodeactive material of the present invention with a conductive material anda binding agent.

The conductive material is added for giving suitable conductivity to theelectrode. This conductive material is not particularly limited, forexample, a carbon black material such as graphite (natural graphite,synthetic graphite, expanded graphite), acetylene black, Ketchen blackand the like can be used.

The binding agent serves the role of binding cathode active materialparticles. The binding agent that is used in this cathode compound isnot particularly limited, however, it is possible to use, for example,polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE),fluororubber, ethylene-propylene-diene rubber, styrene-butadiene,cellulose resin, polyacrylic acid or the like.

It is also possible to add activated carbon to the cathode material, andby added activated carbon, it is possible to increase the electricdouble layer capacitance of the cathode.

The solvent dissolves the bonding agent, and causes the cathode activematerial, conductive material and activated carbon to be dispersed intothe bonding agent. This solvent is not particularly limited, however, itis possible to use an organic solvent such as N-methyl-2-pyrrolidone forexample.

The mixture ratio of the material inside the cathode compound paste isnot particularly limited. For example, when the solid content of thecathode compound without the solvent is taken to be 100 parts by weight,then as in the case of a cathode in a typical non-aqueous electrolytesecondary battery, the content of the cathode active material can be 60to 95 parts by weight, the content of the conductive material can be 1to 20 parts by weight, and the content of the binding agent can be 1 to20 parts by weight.

(Anode)

The anode is a sheet shaped member that is formed by coating and dryinganode compound paste on the surface of a metal foil collector made ofmetal such as copper. This anode is formed essentially by the samemethod as the cathode, however the components of the anode compoundpaste, the composition of those components, and the material of thecollector differ, and as in the case of the cathode, various processingis performed as necessary.

The anode compound paste is formed by adding a suitable solvent to theanode compound, which is a mixture of anode active material and abinding agent, to obtain a paste.

The anode active material, for example, can be a material containinglithium such as metallic lithium or lithium alloy, or can be anabsorbing material that is capable of absorption and desorption oflithium ions.

The absorbing material is not particularly limited, and it is possibleto use an organic compound fired material such as natural graphite,synthetic graphite, phenol resin and the like, or a powder like carbonmaterial such as coke. When this absorbing material is used for theanode active material, as in the case of the cathode, it is possible touse a fluorine-containing resin such as PVDF as the binding agent, andit is possible to use an organic solvent such as N-methyl-2-pyrrolidoneas the solvent that disperses the anode active material into the bindingagent.

(Separator)

The separator is located between the cathode and the anode, andfunctions to separate the cathode and anode and to hold the electrolyte.The separator is made from a thin polyethylene or polypropylene film,for example, it is possible to use a film having a plurality of fineholes, however, as long as the separator has the functions describedabove, it is not particularly limited.

(Non-Aqueous Electrolyte)

The non-aqueous electrolyte is formed by dissolving a lithium salt,which is the supporting electrolyte, in an organic solvent.

The organic solvent can be selected from one kind or a mixture of two ormore kinds of a cyclic carbonate such as ethylene carbonate, propylenecarbonate, butylene carbonate, trifluoropropylene carbonate or the like;a chain carbonate such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, dipropyl carbonate and the like, an ether compoundsuch as tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane andthe like; a sulfur compound such as ethyl methyl sulfone, butane sultoneand the like; or a phosphorus compound such as triethyl phosphate,trioctyl phosphate and the like.

As the supporting electrolyte, it is possible to use a salt such asLiPF₆, LiBF₄, LiClO₄, LiAsF₆, LiN(CF₃S0₂)₂ or a combination of these.

In order to improve the battery characteristics, the non-aqueouselectrolyte can also include a radical scavenger, a surfactant, a flameretardant and the like.

(Characteristics of the Non-Aqueous Electrolyte Secondary Battery of thePresent Invention)

The non-aqueous electrolyte secondary battery of the present inventionis constructed as described above, and has a cathode that uses thecathode active material of the present invention, so a high initialdischarge capacity and a low cathode resistance are obtained, and thebattery is a high capacity and high output battery. Moreover, whencompared with conventional lithium nickel oxide cathode active material,can be said to have high thermal stability and good safetycharacteristics.

(Uses of the Secondary Battery of the Present Invention)

The secondary battery of the present invention has the abovecharacteristics, so it is suitable for use as a power source for acompact portable device that requires constant high capacity (such as anotebook personal computer, mobile telephone or the like).

Moreover, the secondary battery of the present invention is alsosuitable for use as battery as the power source for driving a motor thatrequires high output. As a battery becomes large, it becomes difficultto maintain safety, and expensive protective circuits are essential,however, the secondary battery of the present invention has excellentsafety, so not only is it easy to maintain safety, it is possible tosimplify expensive protective circuits, and further lower the cost. Thebattery can be made to be compact and have high output, so is suitableas a power source for conveying equipment that is restricted byinstallation space.

EXAMPLES Example 1

[Manufacturing of the Composite Hydroxide Particles]

The composite hydroxide particles were manufactured as described below.For all examples, the composite hydroxide particles, cathode activematerial and secondary battery were manufactured using special gradechemicals manufactured by Wako Pure Chemical Industries, Ltd.

(Nucleation Step)

First, water was put into the reaction tank (34 L) until half full whilemixing, the temperature inside the tank is set to 40° C. The inside ofthe tank was air atmosphere (oxygen concentration: 21% by volume). Anappropriate amount of 25% by volume sodium hydroxide aqueous solutionand 25% by volume of ammonia water were added to the water in thereaction tank, and the pH value of the aqueous solution in the reactiontank was adjusted to a value of 13.0 at a standard solution temperatureof 25° C. Furthermore, the ammonia concentration in the reactionsolution was adjusted to be 15 g/L, to obtain the aqueous solutionbefore reaction.

Next, nickel sulfate and manganese sulfate was dissolved in the water toprepare a 1.8 mol/L mixed solution. The mixed solution was adjusted sothat the elemental mole ratio of each metal is Ni:Mn=50:50.

This mixed solution was added at a rate of 88 ml/min to the aqueoussolution before reaction in the reaction tank to form a reactionsolution. At the same time, 25% by volume of ammonia water and 25% byvolume sodium hydroxide aqueous solution were also added at a constantrate to the reaction solution, and with the ammonia concentration in thereaction aqueous solution (aqueous solution for nucleation) constant,control was performed to keep the pH value at 13.0 (nucleation pHvalue), nucleation was performed for 2 minutes 30 seconds.

(Particle Growth Step)

After nucleation ended, only the supply of 25% by volume of sodiumhydroxide solution was stopped until the pH value of the reactionsolution reached a value of 11.6 at a standard solution temperature of25° C.

After the pH value of the reaction solution reached 11.6, the 25% byvolume sodium hydroxide aqueous solution was once again supplied to thereaction solution (aqueous solution for particle growth), and whilekeeping the ammonia concentration at the value above and performingcontrol to keep that pH value at 11.6 at a standard solution temperatureof 25° C., crystallization and particle growth were performed for 30minutes, after which the supply of solution was temporarily stopped, andnitrogen gas was caused to flow at 5 L/min until the oxygenconcentration in the space in the reaction tank become 0.2% by volume orless. After that, the supply of solution was restarted, and from thebeginning of particle growth, crystallization was performed for 2 hours.

When the reaction tank became full, crystallization was stopped, and bystopping mixing and letting the solution sit, deposition of the productwas promoted. After that, after half of the supernatant liquid wasremoved from the reaction tank, crystallization was restarted, and afterperforming crystallization for 2 hours (total of 4 hours),crystallization was stopped.

The grown material was then washed, filtered and dried to obtaincomposite hydroxide particles. Switching from an air atmosphere to anitrogen atmosphere was performed after the start of the particle growthprocess when the time was 12.5% of the total time of particle growthprocess.

During the crystallization above, the pH was controlled using a pHcontroller to adjust the supply flow rate of sodium hydroxide aqueoussolution, and the range of fluctuation was within the range of ±0.2 ofthe set value.

[Analysis of the Composite Hydroxide]

For the obtained composite hydroxide, after a sample was dissolved in aninorganic acid, chemical analysis was performed by using ICP-AtomicEmission Spectrometry, and the composition was found to beNi_(0.5)Mn_(0.5)(OH)_(2+a) (0≤a≤0.5).

Moreover, for this composite hydroxide, the value [(d90−d10)/averageparticle size] that indicates the average particle size and particlessize distribution is calculated and found from the volume integratedvalue that was measured using a laser diffraction scattering particlesize distribution measurement device (Microtrac HRA, manufactured byNikkiso Co., Ltd.). As a result, the average particle size was found tobe 5.3 μm, and the value [(d90−d10)/average particle size] was 0.49.

Next, SEM (scanning electron microscope S-4700, manufactured by HitachiHigh-Technologies Corporation) observation (magnification rate: 1000×)of the obtained composite hydroxide particles was performed, and it wasconfirmed that the composite hydroxide particles were spherical, and theparticle size was nearly uniform. The SEM observation results areillustrated in FIG. 5.

A sample of the obtained composite hydroxide particles was embedded inresin, and after performing a cross-section polishing process, SEMobservation was performed at a magnification rate of 10,000×, and as aresult it was found that the composite hydroxide particles comprisesecondary particles, and those secondary particles were composed of acenter section having needle shape and flake shaped fine primaryparticles (a particle size of approximately 0.03 μm), and an outer shellsection on the outside of the center section having plate shaped primaryparticles that are larger than the fine primary particles (a particlesize of approximately 0.6 μm) were observed. The results of the SEMobservation of this cross section are illustrated in FIG. 6. Thethickness of the outer shell section with respect to the diameter of thesecondary particles was found to be 11% from the SEM observation of thiscross section.

[Manufacturing the Cathode Active Material]

The composite hydroxide particles were heat treated in air (oxygen: 21%by volume) at a temperature of 700° C. for 6 hours, converted tocomposite oxide particles and recovered.

Lithium hydroxide was weighed so that Li/Me=1.35, and then mixed withthe composite oxide particles above to prepare a lithium mixture. Mixingwas performed using a shaker mixer (TURBULA Type T2C, manufactured byWilly A. Bachofen AG (WAB)).

The Obtained lithium mixture was temporarily calcinated in an airatmosphere (oxygen: 21% by volume) at a temperature of 500° C. for 4hours, then calcinated at 900° C. for 4 hours, cooled, and then crushedto obtain the cathode active material.

[Analysis of the Cathode Active Material]

Using the same method as for the composite hydroxide particles, theparticle size distribution of the obtained cathode active material wasmeasured, and the average particle size was 4.8 μm, and the value[(d90−d10)/average particle size] was 0.49.

Using the same method as for the composite hydroxide particles, the SEMobservation and cross-section SEM observation of the cathode activematerial were performed, and it was confirmed that the obtained cathodeactive material was spherical and the particle size was mostly uniform.The results of the SEM observation of this cathode active material isillustrated in FIG. 7. On the other hand, it was also confirmed from thecross-section SEM observation that this cathode active material hashollow construction comprising an outer shell section of sinteredprimary particles, and a hollow section inside the shell section. Theresults of the cross-section SEM observation of this cathode activematerial are illustrated in FIG. 8. The ratio of the thickness of theouter shell section with respect to the particle size of the cathodeactive material was 12%.

The specific surface area of the obtained cathode active material wasfound using a flow type gas adsorption specific surface area measurementdevice (Multisorb, manufactured by Yuasa-Ionics Co., Ltd.) to be 1.5m²/g.

Moreover, analysis by Cu-Kα line powder X-ray diffraction was performedfor the obtained cathode active material using an X-ray diffractometer(X'Pert PRO, manufactured by PANalytical), and the crystal structure ofthe cathode active material was confirmed to comprise a single-phasehexagonal layered crystal lithium nickel manganese composite oxide.

Furthermore, similarly, using the ICP-Atomic Emission Spectrometrymethod, the composition of the cathode active material was analyzed, andconfirmed to be Li_(1.36)Ni_(0.50)Mn_(0.50)O₂ with a composition of Liat 9.55% by weight, Ni at 29.7% by weight and Mn at 27.8% by weight.

[Manufacturing the Secondary Battery]

For evaluation of the obtained cathode active material, the cathodeactive material was used in 2032 type coin battery. As illustrated inFIG. 9, this coin type battery 1 comprises a case 2, and electrodes 3that are housed inside the case 2.

The case 2 has a cathode can 2 a that is hollow and opened on one end,and an anode can 2 b that is placed at the opening section of thecathode can 2 a, and when this anode can 2 b is placed at the openingsection of the cathode can 2 a, a space is formed that houses electrodes3 between the anode can 2 and cathode can 2 a.

The electrodes 3 comprise a cathode 3 a, separator 3 c and anode 3 b,which are layered in this order, and are housed in the case 2 such thatthe cathode 3 a comes in contact with the inner surface of the cathodecan 2 a, and the anode 3 b comes in contact with the inner surface ofthe anode can 2 b.

The case 2 comprises a gasket 2 c, and this gasket 2 c fastens thecathode can 2 a and anode can 2 b so that an electrically insulatedstate is maintained between the cathode can 2 a and anode can 2 b.Moreover, the gasket 2 c also has the function of sealing off the spacebetween the cathode can 2 a and anode can 2 b and closing off the spacebetween the inside of the case 2 and the outside so that the space isairtight and fluid tight.

This coin type battery 1 is manufactured as described below. First, 52.5mg of the obtained cathode active material, 15 mg of acetylene black,and 7.5 mg of polytetrafluoroethylene resin (PTFE) are mixed, and thenthe cathode 3 a is manufactured by pressing the mixture with a pressureof 100 MPa, to a diameter of 11 mm and thickness of 100 μm. Themanufactured cathode 3 a is dried in a vacuum drier at 120° C. for 12hours. Using this cathode 3 a, an anode 3 b, a separator 3 c andelectrolyte, the coin type battery 1 is manufactured inside a glove boxhaving an Ar atmosphere having a dew point controlled at −80° C.

An anode sheet that is formed by coating copper foil with graphitepowder having an average particle size of 20 μm and polyvinylidenefluoride and that is punched into a disk shape having a diameter of 14mm is used as the anode 3 b. A porous polyethylene film having a filmthickness of 25 μm is used as the separator 3 c. A mixed solution(manufactured by Tomiyama Pure Chemical industries, Ltd.) of equalamounts of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1Mof LiClO₄ as the supporting electrolyte is used as the electrolyte.

[Battery Evaluation]

The initial discharge capacity, the cycle capacity retention rate andthe cathode resistance, which are used to evaluate the performance ofthe obtained coin type battery 1, are defined in the following

The initial discharge capacity is the capacity after the coin typebattery 1 is allowed to sit for 24 hours after being manufactured andthe open circuit voltage (OCV) has become stable, is charged to a cutoffvoltage of 4.8 V with the current density with respect to the cathodebeing 0.1 mA/cm², then after stopping for one hour, is discharged to acutoff voltage of 2.5 V.

The cycle capacity retention rate is the calculated ratio of thedischarge capacity after the charging/discharging cycle of charging to4.5 V and discharging to 3.0 V has been performed 200 times, with thecurrent density with respect to the cathode being 2 mA/cm², and theinitial discharge capacity. Measurement of the charge and dischargecapacity is performed using a multi-channel voltage/current generator(R6741A, manufactured by Advantest Corporation).

The cathode resistance is evaluated as described below. The coin typebattery 1 is charged to a potential of 4.1 V, an then using a frequencyresponse analyzer and a potentio/galvanostat (1255B, manufactured bySolartron), the cathode resistance is measured by the alternatingcurrent impedance method, and a Nyquist plot as illustrated in FIG. 10is obtained. This Nyquist plot is represented as a sum of characteristiccurves that indicate the solution resistance, anode resistance andcapacity, and cathode resistance and capacity, so the value of thecathode resistance was calculated by performing a fitting calculationusing an equivalent circuit based on this Nyquist plot.

In performing battery evaluation of the coin type battery having acathode that was formed using the cathode active material above theinitial charge capacity was 208.7 mAh/g, and the cathode resistance was8.2Ω. The capacity retention rate was 85% after 200 cycles.

The characteristics of the composite hydroxide obtained in this exampleis illustrated in Table 1, and the characteristics of the cathode activematerial and the evaluations of a coin type battery that uses thiscathode active material are illustrated in Table 2. The same contentsfor Examples 2 to 8 and Comparative Examples 1 to 5 below are alsoillustrated in Table 1 and Table 2.

Example 2

Except for mixing lithium hydroxide and composite oxide particles weremixed so that Li/Me=1.25, and using a calcination temperature of 850°C., cathode active material for a non-aqueous electrolyte secondarybattery was obtained, and evaluation was performed in the same way as inExample 1. The composition of the obtained cathode active material wasconfirmed to be Li_(1.25)Ni_(0.50)M_(0.50)O₂, where Li was 8.84% byweight, Ni was 29.9% by weight and Mn was 28.0% by weight.

Example 3

Except for switching from an air atmosphere to a nitrogen atmosphere attiming that is 6.25% of the overall time of the particle growth processin the manufacturing process of composite hydroxide particles, cathodeactive material for a non-aqueous electrolyte secondary battery wasobtained, and evaluation was performed in the same way as in Example 1.The composite hydroxide particles, as in Example 1, were composed of acenter section that was made up of needle shaped fine primary particles(particle size is approximately 0.3 μm), and an outer shell section onthe outside of the center section that was made up of plate shapedparticles that are larger than the fine primary particles (particle sizeis approximately 0.7 μm).

Example 4

Except for dissolving sodium tungstate in addition to nickel sulfate andmanganese sulfate in water to form a 1.8 mol/L mixed aqueous solution inthe manufacturing process for composite hydroxide particles, cathodeactive material for a non-aqueous electrolyte secondary battery wasobtained, and evaluation was performed in the same way as in Example 1.This mixed aqueous solution was adjusted so that element mole ratio ofeach metal became Ni:Mn:W=49.25:49.25:0.5. The composition of theobtained composite hydroxide wasNi_(0.4925)Mn_(0.4925)W_(0.005)(OH)_(2+a) (0≤a≤0.5). The composition ofthe obtained cathode active material was confirmed to beLi_(1.36)Ni_(0.4925)Mn_(0.4925)W_(0.005)O₂, where Li was 9.54% byweight, Ni was 29.2% by weight, Mn was 27.0% by weight and W was 0.93%by weight.

Example 5

Except for dissolving zirconium sulfate in addition to nickel sulfateand manganese sulfate in water to form a 1.8 mol/L mixed aqueoussolution in the manufacturing process for composite hydroxide particles,cathode active material for a non-aqueous electrolyte secondary batterywas obtained, and evaluation was performed in the same way as inExample 1. This mixed aqueous solution was adjusted so that element moleratio of each metal became Ni:Mn:W=49.25:49.25:0.5. The composition ofthe obtained composite hydroxide wasNi_(0.4925)Mn_(0.4925)Zr_(0.005)(OH)_(2+a) (0≤a≤0.5). The composition ofthe obtained cathode active material was confirmed to beLi_(1.30)Ni_(0.4925)Mn_(0.4925)Zr_(0.005)O₂, where Li was 9.58% byweight, Ni was 29.3% by weight, Mn was 27.5% by weight and Zr was 0.46%by weight.

Example 6

Except for mixing lithium hydroxide with composite oxide particles sothat Li/Me=1.10, cathode active material for a non-aqueous electrolytesecondary battery was obtained, and evaluation was performed in the sameway as in Example 1. The composition of the obtained cathode activematerial was confirmed to be Li_(1.10)Ni_(0.50)Mn_(0.50)O₂, where Li was7.86% by weight, Ni was 30.2% by weight and Mn was 28.3% by weight.

Example 7

Except for the temperature inside the tank of 50° C. and ammoniaconcentration of 20 g/L, in the manufacturing process for compositehydroxide particles, cathode active material for a non-aqueouselectrolyte secondary battery was obtained, and evaluation was performedin the same way as in Example 1. The composition of the obtainedcomposite hydroxide and cathode active material were the same as inExample 1, and the composite hydroxide particles, as in Example 1, werecomposed of a center section that was made up of needle shaped fineprimary particles (particle size is approximately 0.3 μm), and an outershell section on the outside of the center section that was made up ofplate shaped particles that are larger than the fine primary particles(particle size is approximately 0.7 μm).

Example 8

Except for switching from an air atmosphere to a nitrogen atmosphere attiming that is 25% of the overall time of the particle growth process inthe manufacturing process of composite hydroxide particles, cathodeactive material for a non-aqueous electrolyte secondary battery wasobtained, and evaluation was performed in the same way as in Example 1.The composite hydroxide particles, as in Example 1, were composed of acenter section that was made up of needle shaped fine primary particles(particle size is approximately 0.3 μm), and an outer shell section onthe outside of the center section that was made up of plate shapedparticles that are larger than the fine primary particles (particle sizeis approximately 0.5 μm).

Comparative Example 1

Using a reaction tank for continuous crystallization that is equippedwith an overflow pipe in the top, and while keeping the pH value of thereaction aqueous solution at a constant value of 11.0 at a standardsolution temperature of 25° C. in an air atmosphere, mixed aqueoussolution, ammonia aqueous solution and sodium hydroxide solution werecontinuously added at a constant flow rate, the overflowing slurry wascontinuously collected and crystallization was performed by a typicalmethod. Except for the average residence time in the reaction tank being10 hours, collecting the slurry after the tank was in a state ofequilibrium, performing solid-liquid separation and obtainingcrystallized matter, cathode active material for a non-aqueouselectrolyte secondary battery was obtained, and evaluation was performedin the same way as in Example 1. The composition of the obtainedcomposite hydroxide and cathode active material were the same as inExample 1. The overall composite hydroxide particles were composed ofprimary particles that were the same as in the outer shell section ofExample 1, so the cathode active material was made up of minuteparticles having a solid structure.

Comparative Example 2

Except for the pH value during nucleation and particle growth being keptat a constant value of 11.6 at a standard solution temperature of 25°C., cathode active material for a non-aqueous electrolyte secondarybattery was obtained, and evaluation was performed in the same way as inExample 1. During crystallization, nitrogen gas was caused to flow inthe space of the reaction tank at a flow rate of 5 L/min, to keep theoxygen concentration at 0.2% by volume or less. The composition of theobtained composite hydroxide and cathode active material were the sameas in Example 1. The overall composite hydroxide particles were composedof primary particles that were the same as in the outer shell section ofExample 1, so the cathode active material was made up of minuteparticles having a solid structure.

Comparative Example 3

Except for the pH value during nucleation and particle growth being keptat a constant value of 12.6 at a standard solution temperature of 25°C., nickel manganese composite hydroxide was obtained in the same way asin Example 1. During crystallization, nitrogen gas was caused to flow inthe space of the reaction tank at a flow rate of 5 to keep the oxygenconcentration at 0.2% by volume or less. However, during the entirecrystallization reaction, new nuclei were generated, so particle sizedistribution was wide, and the particles became unstructured withgel-like precipitate, which made separating solid and liquid difficult,so processing was stopped.

Comparative Example 4

Except for the calcination temperature being 1,000° C., cathode activematerial for a non-aqueous electrolyte secondary battery was obtained,and evaluation was performed in the same way as in Example 1. However,as a result of x-ray diffraction measurement, it was found that thehexagonal crystal structure broke down, and performance as a cathodeactive material could not be expected, so battery evaluation was notperformed.

Comparative Example 5

Except for switching from an air atmosphere to a nitrogen atmosphere attiming that is 50% of the overall time of the particle growth processfrom the start of the particle growth process, cathode active materialfor a non-aqueous electrolyte secondary battery was obtained, andevaluation was performed in the same way as in Example 1. The thicknessof the outer shell section of the composite hydroxide particles wasinsufficient, so in the calcination stage of the cathode activematerial, there was sintering of secondary particles, so the activematerial included rough large particles. The composition of the obtainedcomposite hydroxide and cathode active material was the same as inExample 1.

TABLE 1 “Manufacturing Condition and Property of Composite HydroxideParticles” Thickness Timing of Temp. Of Average Outer Ammonia InParticle Switching of Particle (d90-d10)/ Shell Added Concentration TankNucleation Growth Atmosphere Size average Section Elements M (g/L) (°C.) pH pH (%) (μm) particle size (%) Ex. 1 — 15 40 13.0 11.6 12.5 5.30.49 11 Ex. 2 — 15 40 13.0 11.6 12.5 5.3 0.49 11 Ex. 3 — 15 40 13.0 11.66.25 4.9 0.48 13 Ex. 4 W 15 40 13.0 11.6 12.5 5.0 0.48 10 Ex. 5 Zr 15 4013.0 11.6 12.5 5.1 0.49 10 Ex. 6 — 15 40 13.0 11.6 12.5 5.3 0.49 10 Ex.7 — 20 50 13.0 11.6 12.5 6.5 0.51 10 Ex. 8 — 15 40 13.0 11.6 25 5.8 0.528 CE. 1 — 15 40 11.0 (Continuous) — 10.2 0.70 Solid CE. 2 — 15 40 11.611.6 — 9.2 0.63 Solid CE. 3 — 15 40 12.6 12.6 — — — — CE. 4 — 15 40 13.011.6 12.5 5.3 0.49 11 CE. 5 — 15 40 13.0 11.6 50 5.1 0.48 4

TABLE 2 “Manufacturing Condition and Property of Cathode ActiveMaterial” Thickness Capacity (d90- of Retention Average d10)/ OuterSpecific Initial Rate Calcination Particle average Shell SurfaceDischarge Cathode After Li/ Temp. Size particle Section Area CapacityResistance 200 Cycles Me (° C.) Composition (μm) size (%) (m²/g) (mAh/g)(%) (%) Ex. 1 1.35 900 Li_(1.36)Ni_(0.50)Mn_(0.50)O₂ 4.8 0.49 12 1.5208.7 8.2 85 Ex. 2 1.25 860 Li_(1.25)Ni_(0.50)M_(0.50)O₂ 4.8 0.49 12 1.6202.3 8.9 84 Ex. 3 1.35 900 Li_(1.38)Ni_(0.50)Mn_(0.50)O₂ 4.5 0.49 131.3 204.4 8.6 84 Ex. 4 1.35 900Li_(1.38)Ni_(0.4925)Mn_(0.4925)W_(0.005)O₂ 4.7 0.50 11 1.4 205.6 7.2 85Ex. 5 1.36 900 Li_(1.38)Ni_(0.4925)Mn_(0.4928)Zr_(0.005)O₂ 4.7 0.51 111.4 206.8 8.4 87 Ex. 6 1.10 900 Li_(1.10)Ni_(0.50)Mn_(0.50)O₂ 4.8 0.5010 1.5 201.9 10.2 85 Ex. 7 1.35 900 Li_(1.38)Ni_(0.50)Mn_(0.50)O₂ 5.90.53 11 1.5 205.8 8.4 85 Ex. 8 1.35 900 Li_(1.36)Ni_(0.50)Mn_(0.50)O₂5.0 0.55 9.6 1.7 206.6 8.3 83 CE. 1 1.35 900Li_(1.38)Ni_(0.50)Mn_(0.50)O₂ 10.5 0.73 Solid 1.4 208.2 30.5 78 CE. 21.35 900 Li_(1.25)Ni_(0.50)Mn_(0.50)O₂ 8.5 0.68 Solid 1.4 207.1 18.3 81CE. 3 — — — — — — — — — — CE. 4 1.35 1000 Li_(1.26)Ni_(0.50)Mn_(0.50)O₂12.7 0.72 10 1.2 — — — CE. 5 1.35 900 Li_(1.26)Ni_(0.50)Mn_(0.50)O₂ 8.50.74 5.4 1.8 175.3 12.3 —(Evaluation)

The composite hydroxide particles and cathode active material ofExamples 1 to 7 were manufactured according to the present invention, sothe value [(d90−d10)/average particle size], which is an index thatindicates the average particle size and range of the particle sizedistribution, is in the preferable range in all cases, the particle sizedistribution was good and the particle size was mostly uniform. All ofthe cathode active materials comprised an outer shell section in whichaggregate primary particles were sintered, and a hollow section on theinside. Coin batteries in which these cathode active materials were usedhad a high initial discharge capacity, excellent cyclability, and lowcathode resistance, and were batteries having excellent characteristics.

In Comparative Example 1, a continuous crystallization method was used,so nucleation and particle growth could not be separated, and becausethe particle growth time was not fixed, there was a large particle sizedistribution. Therefore, the coin battery had a high initial dischargecapacity, however the cyclability was bad.

In Comparative Example 2, the pH value was 12 or less during bothnucleation and particle growth, so the nucleation amount wasinsufficient, and both the composite hydroxide particles and cathodeactive material had a large particle size. Therefore, the coin batteryhad insufficient reaction surface area, and the cathode resistance washigher than in the examples of the invention.

In Comparative Example 3, the pH value was 12 or greater during bothnucleation and particle growth, so new nuclei were generated during theentire crystallization reaction, and particles became fine andaggregated, and thus the particle size distribution became large andmanufacture of the cathode active material became difficult.

In Comparative Example 4, the manufacturing process of the cathodeactive material is not according to the present invention, so it was notpossible to obtain cathode active material having good characteristics.

In Comparative Example 5, the air atmosphere during the particle growthprocess was long, so the low-density sections became too large and whencreating the cathode active material, the particles became large andrough, so the battery characteristics greatly worsened. The dischargecharacteristic was low, so the cyclability was not measured.

From the results above, it can be seen that by manufacturing nickelcomposite hydroxide particles and cathode active material using themanufacturing method of the present invention, a non-aqueous electrolytesecondary battery that uses this cathode active material has highinitial discharge capacity, excellent cyclability, and low cathoderesistance, and is a battery having excellent characteristics.

Example 9

Except for adjusting the pH value of the aqueous solution beforereaction to 12.8 at a standard solution temperature of 25° C., adjustingthe ammonia concentration in solution to 10 g/L, using a 1.8 mol/L mixedaqueous solution that was obtained by dissolving nickel sulfate, cobaltsulfate, manganese sulfate and zirconium sulfate in water such that themole ratio of the metals was Ni:Co:Mn:Zr=33.2:33.1:33.3:0.5, controllingthe pH value of the reaction solution during nucleation to 12.8,starting the circulation of nitrogen at the start of the particle growthprocess, switching from an air atmosphere to a nitrogen atmosphere (at0% of the overall particle growth process time from the start of theparticle growth process), maintaining the ammonia concentration at thevalue above, controlling the pH value of the reaction solution duringparticle growth to 11.6, performing crystallization for 2 hours, thenremoving half of the supernatant liquid and further performingcrystallization for 2 hours, nickel manganese composite hydroxide thatis expressed as Ni_(0.332)Co_(0.331)Mn_(0.332)Zr_(0.005)(OH)_(2+a)(0≤a≤0.5) was obtained in the same way as Example, 1.

Next, except for performing heat treatment of the obtained compositehydroxide for 12 hours at 150° C., using lithium carbonate as a lithiumcompound to obtain a lithium mixture such that Li/M=1.15, performingtemporary calcination of the obtained lithium mixture for 4 hours at760° C. in air, and performing calcination for 10 hours at 950° C.,cathode active material expressed asLi_(1.15)Ni_(0.332)Co_(0.331)Mn_(0.332)Zr_(0.005)O₂, where Li was 7.93%by weight, Ni was 19.2% by weight, Co was 19.3% by weight, Mn was 18.0%by weight and Zr was 0.45% by weight was obtained in the same way as inExample 1.

Moreover, the obtained composite hydroxide and the cathode activematerial for a non-aqueous electrolyte secondary battery were evaluatedin the same way as in Example 1.

The characteristics of the composite hydroxide obtained in this exampleare given in Table 3, and the characteristics of the cathode activematerials and evaluation of coin batteries that were manufactured usingthe cathode active materials are given in Table 4. The same contents aregiven in Table 3 and Table 4 for the Examples 9 to 12 and theComparative Example 6 to 8.

Example 10

Except for simultaneously and continuously adding sodium tungstateaqueous solution during the reaction crystallization, nickel manganesecomposite hydroxide that is expressed asNi_(0.33)Co_(0.33)Mn_(0.33)Zr_(0.005)W_(0.005)(OH)_(2+a) (0≤a≤0.5) wasobtained in the same way as Example 9, and heat treatment was performed.Except for a calcination temperature of 930° C., cathode active materialexpressed as Li_(1.15)Ni_(0.33)Co_(0.33)Mn_(0.33)Zr_(0.005)W_(0.005)O₂,where Li was 8.07% by weight, Ni was 19.6% by weight, Co was 1.9.7% byweight, Mn was 18.3% by weight, Zr was 0.46% by weight and W was 0.93%by weight was obtained in the same way as in Example 9.

Example 11

Except for changing the pH value to 12.6 and changing the time that themixed aqueous solution is added from 2 minutes 30 seconds to 30 secondsin the nucleation process, starting the circulation of nitrogen 60minutes after the start of the particle growth process, switching froman air atmosphere to a nitrogen atmosphere at 25% the overall particlegrowth process time from the start of the particle growth process, andmaintaining the ammonia concentration at 5 g/L in the nucleation processand particle growth process, nickel cobalt manganese composite hydroxidewas obtained in the same way as in Example 10, after which heattreatment and calcination were performed to obtain cathode activematerial. The composition of the obtained composite hydroxide and thecathode material were the same as in Example 10.

Example 12

Except for performing adjustment of the composite hydroxide so that thecomposition of Ni, Co and Mn became x=0.50, y=0.25 and z=0.25, the samenickel manganese composite hydroxide was obtained. Except for the anLi/M ratio of 1.05, calcination conditions of 850° C. and 10 hours,cathode active material expressed asLi_(1.05)Ni_(0.495)Co_(0.248)Mn_(0.247)Zr_(0.005)W_(0.005)O₂, where Liwas 7.19% by weight, Ni was 28.7% by weight, Co was 14.4% by weight, Mnwas 13.4% by weight, Zr was 0.45% by weight and W was 0.91% by weightwas obtained in the same way as in Example 1.

Example 13

Cathode active material that was obtained in the same way as in Example9 was dried in a fluidized drier (Powrex Corp.; MP-01) at 180° C. whileblowing hot air and causing sodium tungstate solution to be sprayed, anda cathode active material, the surface of which is coated with sodiumtungstate, obtained. The composition of the obtained active material isthe same as in Example 10, and through SEM observation of this crosssection by EDX diffraction, it was confirmed that there was muchtungsten on the surface of the active material particles.

Example 14

Except for dispersing composite hydroxide that was obtained in the sameway as in Example 9 into ammonium tungstate solution to 150 g/L, turningthe solution into a slurry, and spray drying that slurry by using amicro mist dryer (Fujisaki Electric Co., Ltd; MDL-050M) to obtain acomposite hydroxide that is coated with ammonium tungstate salt, cathodeactive material was obtained in the same way as in Example 10. Thecomposition of the obtained active material was the same as in Example10, and through SEM observation of this cross section by EDXdiffraction, it was confirmed that there was much tungsten on thesurface of the active material particles.

Comparative Example 6

Except that the calcination conditions were 1050° C. and 10 hours, acomposite oxide cathode active material was obtained in the same way asin Example 9. Sintering proceeded at a high calcination temperature, sothe specific surface area was low, and the cathode resistance valuebecame high.

Comparative Example 7

Except for causing nitrogen to flow during the crystallization reactionin the nucleation process and particle growth process, and using anon-oxidizing atmosphere (oxygen: 0.2% by volume or less), cathodeactive material was obtained in the same way as in Example 10.

The overall composite hydroxide particles were composed of the same kindof primary particles as the outer shell section in Example 10, and thestructure of the cathode active material was dense, so the specificsurface area was low, and the cathode resistance became high.

Comparative Example 8

Except for causing nitrogen to flow during the crystallization reactionin the nucleation process and particle growth process, and using anon-oxidizing atmosphere (oxygen: 0.2% by volume or less), a lithiumnickel cobalt manganese composite oxide was obtained in the same way asin Example 12.

The overall composite hydroxide particles were composed of the same kindof primary particles as the outer shell section in Example 10, and thestructure of the cathode active material was dense, so the specificsurface area was low, and the cathode resistance became high.

TABLE 3 “Manufacturing Condition and Property of Composite HydroxideParticles” Thickness Timing of Temp. Of Average Outer Ammonia InParticle Switching of Particle (d90-d10)/ Shell Added Concentration TankNucleation Growth Atmosphere Size average Section Elements M (g/L) (°C.) pH pH (%) (μm) particle size (%) Ex. 9 Zr 10 40 12.8 11.6 0 3.9 0.4935 Ex. 10 Zr, W 10 40 12.8 11.6 0 4.3 0.46 35 Ex. 11 Zr, W 5 40 12.611.6 25 4.6 0.46 11 Ex. 12 Zr, W 5 40 12.6 11.6 25 6.1 0.51 13 Ex. 13Zr, W 10 40 12.8 11.6 0 3.9 0.49 35 Ex. 14 Zr, W 10 40 12.8 11.6 0 3.90.49 35 CE. 6 Zr 10 40 12.8 11.6 0 3.9 0.49 35 CE. 7 Zr, W 10 40 12.811.6 — 4.2 0.50 Homo* CE. 8 Zr, W 5 40 12.6 11.6 — 6.5 0.53 Homo* Note:Homo = Homogeneous

TABLE 4 “Manufacturing Condition and Property of Cathode ActiveMaterial” Thick- ness Capacity (d90- of Retention Average d10)/ OuterSpecific Initial Rate Calcination Particle average Shell SurfaceDischarge Cathode After Li/ Temp. Size particle Section Area CapacityResistance 200 Cycles Me (° C.) Composition (μm) size (%) (m²/g) (mAh/g)(%) (%) Ex. 9 1.15 950Li_(1.18)Ni_(0.332)Co_(0.331)Mn_(0.332)Zr_(0.005)O₂ 4.5 0.51 36 1.2155.1 4.4 91 Ex. 10 1.15 930Li_(1.15)Ni_(0.25)Co_(0.32)Mn_(0.33)Zr_(0.005)W_(0.005)O₂ 4.6 0.46 361.6 154.7 4.0 92 Ex. 11 1.15 900Li_(1.16)Ni_(0.23)Co_(0.35)Mn_(0.58)Zr_(0.005)W_(0.005)O₂ 4.7 0.49 121.8 156.7 3.9 93 Ex. 12 1.05 850Li_(1.05)Ni_(0.495)Co_(0.243)Mn_(0.247)Zr_(0.005)W_(0.005)O₂ 6.2 0.50 141.1 170.2 4.4 88 Ex. 13 1.15 950Li_(1.15)Ni_(0.33)Co_(0.33)Mn_(0.23)Zr_(0.005)W_(0.005)O₂ 4.5 0.50 361.3 155.0 4.1 92 Ex. 14 1.15 950Li_(1.15)Ni_(0.33)Co_(0.32)Mn_(0.33)Zr_(0.005)W_(0.005)O₂ 4.4 0.51 361.2 155.3 4.2 91 CE. 6 1.15 1050Li_(1.15)Ni_(0.332)Co_(0.321)Mn_(0.352)Zr_(0.005)O₂ 11.5 0.92 45 0.42141.4 8.6 — CE. 7 1.15 930Li_(1.15)Ni_(0.33)Co_(0.23)Mn_(0.33)Zr_(0.005)W_(0.005)O₂ 4.4 0.51 Solid0.85 155.6 5.1 90 CE. 8 1.05 850Li_(1.15)Ni_(0.495)Co_(0.248)Mn_(0.247)Zr_(0.005)W_(0.005)O₂ 6.2 0.51Solid 0.6 170.7 5.5 89

INDUSTRIAL APPLICABILITY

The non-aqueous electrolyte secondary battery of the present inventionis suitable as a power source for compact electronic devices (notebooktype personal computer, mobile telephone, and the like).

Moreover, the non-aqueous electrolyte secondary battery of the presentinvention has excellent safety characteristics, is compact and has highoutput, so is suitable for use as a power source of conveying equipmentwith hunted space.

EXPLANATION OF REFERENCE NUMBERS

-   1 Coin type battery-   2 a Cathode can-   2 b Anode can-   2 c Gasket-   3 Electrodes-   3 a Cathode-   3 b Anode-   3 c Separator

What is claimed is:
 1. A cathode active material for a non-aqueouselectrolyte secondary battery comprises lithium nickel manganesecomposite oxide particles having a layered hexagonal crystal structureand expressed by a general formula of Li_(1+u)Ni_(x)Mn_(y)Co_(z)M_(t)O₂(where −0.05≤u≤0.50, x+y+z+t=1, 0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1,M is one or more added elements that are selected from among Mg, Ca, Al,Ti, V, Cr, Zr, Nb, Mo and W), the cathode active material having anaverage particle size of 2 to 8 μm, a value [(d90−d10)/average particlesize], which is an index indicating an extent of particle sizedistribution thereof, of 0.60 or less, and having a hollow structureprovided with an outer shell section of aggregated sintered primaryparticles and a hollow section inside the outer shell section, wherein aratio of the thickness of the outer shell section with respect to theparticle size of the lithium nickel manganese composite oxide particlesis 5 to 45%.
 2. The cathode active material for a non-aqueouselectrolyte secondary battery according to claim 1, wherein the ratio ofthe thickness of the outer shell section with respect to the particlesize of the lithium nickel manganese composite oxide particles is 8 to38%.
 3. A non-aqueous electrolyte secondary battery, the cathode thereofbeing formed using the cathode active material for a non-aqueouselectrolyte secondary battery according to claim
 1. 4. The cathodeactive material for a non-aqueous electrolyte secondary batteryaccording to claim 1, wherein the average particle size is 3 to 6.5 μm,and the value [(d90−d10)/average particle size] is 0.55 or less.
 5. Thecathode active material for a non-aqueous electrolyte secondary batteryaccording to claim 1, wherein the ratio of the thickness of the outershell section with respect to the particle size of the lithium nickelmanganese composite oxide particles is 8 to 14%.
 6. The cathode activematerial for a non-aqueous electrolyte secondary battery according toclaim 1, wherein the absolute value of the thickness of the outer shellsection is 0.5 to 2.5 μm.